The identification window is the sum of relative and absolute window, applied symmetrically to the expected retention time. For example:
Expected retention time = 1 min
Absolute retention time window = 0.2 min
Relative retention time window = 10 % = 1 min * 10/100 = 0.1 min
Identification window = [1 - 0.2 - 0.1 ; 1 + 0.2 + 0.1] = [0.7 ; 1.3]