A contrast budget can compare two finite waits without fitting an exponential. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The first finite wait retains three fourths
With the first declared wait, 60 of 80 shots remain, so the retained fraction is 3/4.
ffirst=43
The longer declared wait retains one half
The contrast budget keeps 40 of 80 shots, so the fraction is 1/2.