It's not 50 macros, it's concurrently executing instances. And even that's not the full story -- if you have a recursive macro then each level of recursion accounts for 2 executing instances, each level of "nesting" (the "Group" Action, the "If... Then... Else" Action, and so on) also counts as an executing instance (I think -- I'm never sure where the line is drawn).
So yes, I'm sure you've often hit 10 -- though maybe not 50!
If you do want to see what happens when you break the limit (check the Engine log) have a play with my recursive String Reversal demo.