Moving through the tiers is a one-way door... if you get to a certain point you are promoted to the next tier... then, as everything is a bit harder, your average may go back UP, but you can NOT be demoted.
So, you can theoretically see a Master with a 100 average...
Don't get hung up on labels... play your best game, post all your scores, and when you're ready to move up, you will move up.
Peace.