e1608: cosmetic minors -- 2-digit frequency spin, smaller mock catch-up cap, docs wording

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -142,8 +142,8 @@ trigger is configured, so as not to reset the wait for the edge; this is unverif
 numbering (channel + 8) and the filler byte after scan start are agreed by both references. The scan overrun count
 is approximate: the board does not say how many scans it dropped, so the frame after a restart reports one lost.
 Errors (no device, a rejected connection code, a timeout, the scan socket closing) are written to stderr as
-`[e1608] ...` once per distinct message; the window shows only that the source is disconnected (the status popover
-reads `waiting`, and the panels go insensitive), not why.
+`[e1608] ...` once per distinct message (an overrun is logged each time it happens); the window shows only that
+the source is disconnected (the status popover reads `waiting`, and the panels go insensitive), not why.
 
 A session file written before kinds existed has no `source_kind`, and is read as UDPS; a UDPS file is
 written exactly as before. A kind's capability panels (for instance a source's own controls) appear as