Jimbog1964:More to the point can I tell how many games I have played as Legend? I only care because with my new enthusiasm for notes I want to see how my averages start to turn. As I understand it you can more or less do as you will for 450 rounds as Legend but then they really count???
It will be hard to tell exactly how many Legend rounds you have but I think it's not of primary importance. As others said, you will notice when you have arrived at 500 by "irregular", more precisely non-linear reaction of the average. It will drop sharply, it will drop on scores above the average - for a while. Most important: It is saturated then, and it will never rise again as long as you are a Legend. (1)
When you notice such jumps, save the no. of ranked rounds from your stats if you wish so, count off 500 to have a fair impression of your first Legend round. OTOH, it doesn't really matter in the future :)
Second point is, all of your Legend rounds from day one on are eligible for your average. Alas, only the best 500 scores will be selected for the calculation. After saturation, you need to play a score better than the worst of those to influence it.
Thinking the other way round, you'll tier up when you have played 500 Legend scores forming an average of 60.000 or better - none of the worse rounds has any effect.
(1) Counting and calculations re-start from scratch when you become Tour Legend.