Relegation is to be demoted from your league, into a lower level league.
4 teams from each league will relegate:
the two 8th place teams in each conference automatically do so.
Then, the 6th and 7th place teams from opposite conferences play a relegation series. The winner of the 3 game series gets to stay in their league, the losers relegate.
Note that in USA D.V, there will be a relegation series, but you won't actually demote into DVI. USA Division VI is all bots.