A replicate mean is accepted only after its spread gate closes. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Spread is checked before the mean is trusted
The maximum minus minimum is 4. The half-range is 2.
Δr=4,Δr/2=2
The boundary counts as a pass
The spread limit is 2. Since the half-range is equal to the limit, the gate passes.