Phase loss is a finite coherent/dephased ledger, not an exponential fit. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Phase loss splits coherent from dephased shots
Out of 100 phase-sensitive shots, 60 remain coherent and 40 are dephased.
60+40=100
Only the coherent fraction scales visibility
The coherent fraction is 3/5, so an ideal visible count of 50 becomes 30.