Meetme event $data['duration'] vs MASTER.CSV duration

meetme event $data[‘duration’] vs MASTER.CSV duration

Why would these values of duration of call be different by something like 5 - 8 seconds ?

Seems like one would be from start of ring or before conference number vetted … and the other might be from conference number input onwards. Someone … please advise on how to distinguish between these … I would think the KEY name should be different.