It has been explained - let me have another try...
texbbqman: My avg this am was 61.0.
Which equals -11 on STA.
texbbqman: Afterwards I played St Andrews at -10.
A 62, true. Was the score better than the average? Which change of your average do you expect from these numbers?
texbbqman: Tonight I sign on to play and my avg is now 62.1. Anyone have an idea what happened??
This is what happens to a linear average when you add higher values: It rises.
It's also safe to say that your average is not yet saturated (500 Legend rounds), meaning that you must play lots of regular ranked strokeplay to get to the next stage. Also, 32/64 and 33/66 scores won't help you much to arrive at 60.000 ave. or lower for the next tier.
Plenty of grinding before you - don't mind the average now, just have fun!