Three flip fractions separate channel error rate from source shot count. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
One tenth flip moves ten shots
The source total stays 100. A flip fraction of 1/10 moves 10 shots into the one bucket.
100⋅101=10
One fifth flip moves twenty shots
The base channel fraction 1/5 moves 20 shots and leaves 80 shots in zero.
100⋅51=20
Three tenths flip moves thirty shots
At flip fraction 3/10, the same 100 source shots produce 70 zero and 30 one shots.