Even par is not a constant number.
Some courses are par 70, some are par 71, and some are par 72.
By the same token each 9 can have a different par. Olympic is a classic example in that each 9 has different par. One Olympic 9 has a par that is 2 strokes higher than the other 9.
When you move up a tier your stroke average is based on zero scores until you play a ranked round and post your first score at the new tier.
The first score you posted at the Master tier was a 36 you shot on the front 9 at Kiawah. As pointed out above, 2 x 36 = 72, and that became your Master tier stroke average.
It takes 40 ranked rounds to 'saturate' your Master tier stroke average. So until you post 40 ranked round scores your stroke average can go both up and down based on the initial 40 scores you have at the Master tier. With score #41 your score average will no longer be able to go up. It will only stay the same, or go down if you make a ranked round score that is lower than your stroke average.
NOTE: In some types of multiplayer games (Match Play Challenges for example), wins against higher tier opponents can also lower your score average but WGT does not say by how much.