It's based on the higher of two groups based on last 3 weeks.

So if you met the requirement say 2 and half ago, you will have 6 this time. But if you haven't met it since, you will drop to 3 on the next fight.

Alternatively, your opponent in prelim could be the one that qualified, thus you got 6 there. Whereas your group doesn't, thus getting 3 against other opponents.

And finally the group "no opponent" qualifies by default.