MR8
The FDP stops at chocks on, the duty period AT LEAST 30 minutes after that. If you are delayed at the aircraft for wheelchairs or so, just make a note on when your duty stopped.
It's really all in the OM-A chapter 7, and not too difficult.
Actually MR8 there is no reference to the 30 min after chocks on in Ch 7 for pilots.
It is only in the CABIN crew section of chapter 7.