Wow, 20 follies is really good mumof5.
Mine were the same, started off small and then they grow quite rapidly (although not all evenly).
From my limited experience, I dont think they like them to get beyond 22 as this may risk OHSS.
The number of follies may also not correlate to the number of eggs collected as some may not be mature enough.
My first scan, I had 10 follies, the next 17 follies, and only 8 eggs were ultimately collected 6 of which fertilised.
Have my fingers crossed for a good result - and hope the u/s wasnt too uncomfortable.
V