The answer is in "Changing Tiers" over there ==>
How do I change tiers?
Advancing to the next Tier requires a qualifying Average Score AND a minimum amount of completed stroke play games,
Frequently, those with an average lower than the limit score work the system to their profit (sandbagging) and therefore the numbers aren't published officially. The best guesses for the advancement to Tour Pro are a 72 average calculated over 20 minimum rounds though.
Numbers will reset after the tier change.