Undoing with /rewind
/rewind with no argument restores your working tree to exactly how it was before the most recent file-changing turn started. Anything that turn created is deleted; anything it edited or deleted is restored to its prior contents, precisely.
/rewind 3 goes back further in one step, undoing the last three file-changing turns at once rather than one at a time, useful when a short sequence of turns together produced a result you want to abandon entirely.
Before actually restoring anything, tCode always tells you exactly which turn a given rewind is about to restore to and asks you to confirm, so undoing several turns at once is never a guess about what you are actually about to lose.
Confirming a rewind is the last step, not a two-stage process; once confirmed, the restoration happens immediately and the working tree reflects the earlier state right away, ready to continue working from.
There is no upper bound baked into /rewind beyond how many checkpoints genuinely exist in the current session; /rewind 10 works the same way as /rewind 3, it simply walks back further, as long as that many checkpointed turns actually happened.