docs: document PR #1385 rounding behavior

docs/CURRENT-STATE.md

@@ -4133,6 +4133,9 @@ and as the last line of the list, because the arrival step is among the ones
 dropped. A route of exactly 200 is complete, and a roundabout exit after the
 200th keeps folding into it.
 
+Route duration labels select their unit after rounding seconds: a leg of
+59.5 seconds or more displays as `1 min`, rather than `60 s`.
+
 A step's card opens from its dot on the globe or from its line in the list, and
 the list covers every step including departure and arrival, which have no dot.
 What a card needs is a resolved ground anchor: a step whose ground cell has not