CWA 7.3.2 e): "The assigned accumulated duty hours (based on the published working timetable or on the rostered ground duty) must not exceed 30 hours in any period of 3 consecutive days. This rule also applies when called out of standby duty;"

It is the planned or "published working timetable" time that is used, not the actual time. If you are early or have delay does not change the calculation.