That's the "old" way of calculating the tier advancements. And despite Pizza, it was VERY accurate. These days....not so much. Playing match play games vs players in a higher tier, and winning, affects your average much more.....and the minimum ranked rounds don't count from match play. Ready Go's are also rumored to affect your average more severely now, too.
So, advancing really requires this, Scott.......
- Continually improving your average....by whatever means.
The numbers above are important milestones to aim for and watch, but they aren't the end-all and be-all anymore. I've seen players very close but still not make advancement, and I've even seen a TourMaster with an average of 60.0. That wasn't possible in the old days (unless he had very few ranked rounds). This player told me he had been TM for 3 months......almost impossible by today's standards.
So, just do what you do and the promotions will follow in time.