Holding separation fixed makes endpoint signal difference the gradient source factor. 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 six-signal difference over six metres gives one per metre
Hold left signal at 6 and separation at 6 m. Right signal 12 leaves difference 6 and gradient 1 per metre.
6/6=1
A twelve-signal difference gives two per metre
Right signal 18 makes difference 12. Over the same separation, gradient is 2 per metre.
12/6=2
An eighteen-signal difference gives three per metre
Right signal 24 leaves difference 18 and gradient 3 per metre. This is a one-dimensional toy signal ledger.