30 minutes
The 30 minutes after the duty is exactly the same as EASA. 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. It might help if you actually read the chapter once in a while, it is the most important one in the book.
And BTW, we are not paid for any flown duty, we are paid for scheduled block time...