Redemption period
Also: redemptionPeriod
The 30-day window, documented by ICANN, during which a deleted domain is held before it moves to pending-delete and is eventually released.
The redemption period plus the pending-delete window is where the roughly 35 days between a zone exit and a domain becoming available comes from. A domain in redemption can still be restored by its registrar, which is why an exit is a watchlist entry rather than a purchase.