Oldstir:
You're not alone. At Master tier, I was at 63.8 average and then I shot a 13 under par 59 on OAK and that only brought my average down to 63.63. I couldn't believe it and as it turned out; I had to shoot another 11 ranked rounds of 65,66,68,64,64,61,64,64,63,62 and 62 before my average became 63.0 exactly to reach the Tour Master tier. And if you notice, the average of those 11 rounds is only 63.9. So how the heck did that qualify me to reach exactly a 63.0 average but a "13 under" wouldn't????? Makes no sense to me. Anyway, it took me over 100 ranked rounds plus a few 9-hole really good sub par rounds before reaching TM. And that was all done before I reached Level 88 which allowed me to buy the R11 9.0 Driver. So if You were shocked that 6 under didn't get get you under a 63 average; just imagine how stunned I was that "13 under" didn't get me under a 63 average. :) So I guess he's right that it takes a 63.0 average to reach TM. But how they figured my last 11 rounds averaging 63.9 as a Master; all of a sudden, somehow becomes exactly a 63.0 average, is beyond me.
However, as I understood, any Tournament scores or Match-play scores Never count toward your regular ongoing average. So even if you shot a 9 under in that Ready Go tourney, it would not be used toward calculating your ongoing average but I could be wrong.
The Master average counts only your best 40 rounds.
When your average was at 63.8, the worst ranked round in your best 40 Master rounds was a 66. In fact, you had at least 10 66s in your best 40.
Your 59 replaced a 66, knocking 7 strokes off your 40 round total. 7/40 = .175, which after rounding is why your average went down .17.
You then had 9 more rounds that replaced 66s. The total of those rounds was 569, the total of the 66s they replaced was 594. 594-569=25, and 25/40=.625, the amount needed (after rounding, here you get the .005 back that you "lost" before) to get you to 63.0.
Tournament and Ready-go scores definitely count towards an average.
Now that you're at Tour Master, your average will be calculated for your best 50 rounds.