Nearly everyone was at the first meetup for the full scheduled time period. I would guess at least 5-6 people to be there if you show up at any given time during the window, given that 13 were there for the most of it. We dispersed when it got under 5, about an hour after the scheduled end.

(I'm throwing out these nudges because I prefer not to have a shorter scheduled timespan, so that people pencil it in for more of their time, leading to an increase in quantity people*time instead of just people.)