A drift window bound propagates baseline uncertainty into a range of possible net signals rather than a single corrected value. The measured signal is 20 while the baseline window is [4, 6], so the net signal falls in [14, 16] with interval width 2 exactly for the stated toy drift ledger; real instruments have nonlinear drift, environmental variation, and calibration uncertainty.
A drifting baseline creates an exact net interval. 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 drifting baseline is an interval
The measured signal is 20, while the baseline can be between 4 and 6.
B∈[4,6]
The net signal becomes a checked interval
Subtracting the high baseline gives 14; subtracting the low baseline gives 16. The interval width is 2.