Thanks to all for your help. The show was fun!
For those curious - I rushed Sunday (5/

and got there just after 7:30 (wanted to be safe since it was Mother's Day). My friend and I were first in line. Next person in line was at 8, but after that people steadily came. By 8:45ish I'd say, we'd filled the 14 rush seats. Line continued to grow to at least 30 people. Not sure what happened after the 14 seat were sold as I'd heard the show was pretty much sold out for the Mother's day weekend (it was not on TKTS Sat or Sunday).