The types are average, top, bottom, min, max, peak to peak, amplitude, above, below, between, pulse duration, period and frequency. top and bottom are the waveform's flat high and low levels: the level the signal dwells at, taken from the densest band of the window on each side of the split. A band-limited edge overshoots and rings — a nominal 2 V square reaches about ±1.18 at its edges — and a ripple or an overshoot is therefore not what these read. amplitude is the delta between those two levels, and peak to peak is the swing between the extremes (so on a rippled square amplitude reads 2 V where peak to peak reads 2.36 V).

above, below and between are the opposite kind of number: the plain mean of the samples above a share, below it, or between two shares. That is a different question from top/bottom even about the same split, and it is the older one — on a unit sine above 50% reads 0.64 V (2/π, the mean of a half cycle) where top reads 0.96 V (near the peak, which is where a sine dwells most), and on a band-limited square above 50% reads 0.99 V where top reads the plateau, 1.00 V: the edge's ring is inside the first and not inside the second. between takes two shares — from % and to % — and reports the mean of the samples inside that band, which no single split can answer; the order you type them in does not matter, since a band between 80 % and 20 % is the band between 20 % and 80 %.

A mean over a side carries whatever is on that side, so these three are the right numbers when you want the energy or the offset of part of the waveform, and the wrong ones when you want the level a plateau sits at. Like every other measurement, one with nothing to measure reads -- rather than a made-up number: a share at 100 % has no sample above it, and a band can hold none at all — on an ideal (non-ringing) square every sample is exactly ±1, so a band between 50 % and 75 % is empty.

top and bottom also read near the peak on a waveform that has no flat part, which is the honest reading rather than a failure: a unit sine has no plateau, so the densest band is at its peak and these read about ±0.96 — not the 0.64 a mean over each half would give, and not ±1 either. Only a level the signal actually dwells at is a level.

The split says which side a level is read from, so any share between the two levels reads the same number; it is not a boundary the value depends on. The one case where it is read directly is a window the scope cannot summarize by level — a window shorter than a level's own resolution, or one read through hf — where top/bottom fall back to the mean of each side of the split and amplitude to the window's peak to peak.

The on-plot marks come in two kinds and the mix is the reading: a level mark is a ruler at a value, a time mark is a marker at a position. An average draws one level mark; a max draws a level mark and a time mark at the first sample that reached it; peak to peak draws a ruler at each extreme and amplitude a ruler at each of its two flat levels — the pair is the span, so the two rulers are the measurement.

Marks cannot be dragged. A measurement mark says what the measurement measured, so it is created unselectable — as is the trigger marker.

A pass is throttled to a cadence rather than run every frame, so a ruler over a live view is stepped. The number and the ruler come from the same pass, so they always agree.

An invalid pass keeps its level marks and drops its time marks. A level is a property of the signal and outlives the window; a position inside the window does not. That is what stops the rulers blinking off at a mode change.

A crossing is counted with hysteresis, not on a bare level: the thresholds are a tenth of the window's peak to peak either side of the share, and an edge is counted only once the signal has passed the far one. Period, frequency and pulse duration all depend on it. The mid level is exactly where a waveform moves fastest, so any interferer faster than the fundamental recrosses a single level several times per real crossing — a 5 Hz sine with a 500 Hz tone at a tenth of the amplitude reads 39 Hz without the band and 5 Hz with it. The band holds to an interferer a third of the waveform's own size.

The band is clamped to stay inside the data, which is what keeps a threshold set near an extreme usable: a fixed band there would sit above every sample and the measurement would read nothing. A share near an extreme still leaves the band little room, so it rejects less — which is one reason period and frequency offer no share to set.

A window with too few crossings reads invalid / -- rather than a plausible invented number. Frequency over a window holding one edge is the usual case.

frequency is reported in Hz and period/pulse duration in seconds; every other type carries the channel's own unit. A value is written with a metric prefix so its digits sit in 1..999 — 636.62 mV, not 0.64 V — including when the stream declares no unit at all, which is always the case for a math channel: there the prefix goes tight against the number (636.62m), since two decimals of an unprefixed small value is 0.00.

Cost is bounded by reading the summary pyramid the producer already maintains, not the raw window: a bucket's sum is a sum, so the mean, the extremes and a level's own mean are exact. top, bottom and amplitude read the density of the window out of that same summary — which is what tells a flat level from a ripple — so those three cost a second read of the summary and never of a sample, and between's second share is one more level in the same summary walk rather than a walk of its own.

Statistics adds a second line to every measurement showing n, the mean, the standard deviation and the range. Each observation is one recompute of the pane, so n counts windows measured, not samples — a mean frequency over many windows is what that claims to be. Reset clears every accumulator and starts fresh. A change of display window, a CONFIG or a measurement edit also resets; a pause, a resume, a zoom, a pan and the toggle itself do not, so turning the line off to read the plot and back on again keeps the history. On a still frame a pan or a zoom changes nothing for the history to record in the first place — the values do not move there at all.