Elapsed [from, to] window into the activity, in seconds — the time anchor
a contiguous Focus / range annotation maps onto.
Cumulative-distance window [start, end] into the activity (metres) — the anchor for a map-segment highlight, the distance-axis peer of from/toSeconds.
Average speed — the recorded average when present, else distance ÷ moving
time. undefined only when neither is available (no distance / no time).
A range of an activity with its own analytics — a split, a lap, or a slice. Quantity-typed views over a SectionMetrics bundle; nothing computes here (the producer already did), so accessors are pure getters.