Four repeated readings form a finite measurement ledger, and the average gives the center of that stated sample. The arithmetic is exact only for the listed readings and gate rule; real measurements can include correlated noise, resolution limits, calibration drift, outliers, and sampling bias.
A repeated reading gate is an exact residual ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Four readings average to the target
Readings 9, 11, 10, 10 volts average to 10 volts.
Vˉ=49+11+10+10=10V
Residuals make the acceptance finite
Against target 10 volts, residuals -1, 1, 0, 0 give squared budget 2, which is within limit 4.