Time on the ground
Rustle, I understand your "6 minutes before t/o, 6 minutes after" -that's trying to reflect what I always understood should be used in the logbook - "the time in command of the aircraft".
Having crawled down the taxiway at Elstree once on a busy day for over 20 minutes, which I logged, I'm not even sure your "6 minutes" is always enough ...