The timer serves the repetition. Start with enough recovery for clean work, then shorten it gradually rather than guessing each set.
Small upper-body isolation work may recover quickly. Large lower-body compounds often need longer for breathing and bracing to settle.
If the next set loses range or shifts away from the target, the interval is below its useful floor.
Pump Ledger is a training logbook, not medical advice. Scale training to your experience and circumstances, and seek qualified guidance when health or injury concerns affect exercise.