A later readout fails the same finite-window check. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A waiting stage still counts against the window
The late sequence includes a wait of 5 seconds between prepare and control.
twait=5
The total misses the declared window
The elapsed time is 14 seconds, which is larger than the 10 second coherence window.