An ideal RF control line is checked as on and off windows. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Control windows have endpoints
The first RF window runs from 0 s to 2 s. The second runs from 6 s to 8 s.
ttotal=10s
Duty fraction is active time over total time
The active time is 4 s out of 10 s, so the duty fraction is 2/5. This is a control schedule, not a spin-rotation model.