Function

finishThresholdSeconds

finishThresholdSeconds(durationSeconds: number): number
The position, in seconds, at which a lesson counts as watched to the end.
Parameters
- durationSeconds: number
  The lesson's length
Returns number
The threshold in seconds; meaningless for a duration of <= 0, which hasFinishedWatching rejects before reaching here
Remarks
The earlier of the two rules in SECONDS_FROM_END. For a clip shorter than the fixed tail, durationSeconds - SECONDS_FROM_END is zero or negative — a threshold no position could fail to cross — so the percentage rule takes over and a finish stays reachable but earned.
Example
```
finishThresholdSeconds(600); // 570 — the percentage rule wins
finishThresholdSeconds(60);  // 45  — the fixed tail wins
finishThresholdSeconds(10);  // 9.5 — the tail would be negative
```
- Defined in lib/watch-progress/watch-progress.ts:50