Your theoretical one-rep max, estimated from a set you actually did.
Estimated 1RM
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Epley: 1RM = weight × (1 + reps ⁄ 30). It is the one REPWIND uses in the app, over the best set of each session.
The estimate holds between 1 and 10 reps. Past that, endurance outweighs strength and the gap widens — a set of twenty says more about how long you last than how much you lift. It also depends on the movement: a squat and a curl do not lose force at the same rate as reps climb.
Above all, a formula applied to your best day overstates what you will do on an ordinary Tuesday. That is why the app builds its estimate from every set you really did rather than from a single record.