A: The Future Doctor is always exactly one higher than the highest numbered Doctor in the game (not the highest numbered Doctor in play, but the highest numbered one in the deck). So, for purposes of the Goal Regeneration, the Future Doctor consecutively follows the highest numbered Doctor in the game.

Imagine all the Doctors are waiting in a queue. The Future Doctor is always behind the last Doctor in line. So if Peter is the last Doctor in line, the Future Doctor is next in line behind Peter. And when Jodie joins the line, she’s behind Peter, and the Future Doctor is behind her.