Your "average" is based on the rounds you have played the the tier you are in. When you went up a tier, the number of rounds reset to 0. You shot a 41 for 9 holes which equates to an 82 for 18. this was your first round as a Master so it became your new "average".
Your 41, 37, and 70 scores as a Master equal 226 shots or your average of 75.33 per round. (226 divided by 3)