A crosstalk channel moves counts across lanes by an exact declared direction. 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 neighbor channel can move lane a into lane b
Starting from 50 in lane a and 50 in lane b, one fifth from lane a gives 40 and 60.
Nforward=(40,60)
The reverse contrast is a different declared channel
If the moved fifth comes from lane b instead, the output becomes 60 in lane a and 40 in lane b.