As to the number of people present on the day, I counted 10 rows of chairs with 10 chairs in each row, this said, there was I guess just as many standing around the edges as the number of people seated. So at least 200.
Since the room was filled beyond capacity, (fire drill max 190), th session was repeated at 14:00. with what seem to me just about the same amount of people..
My best guess therefore is +400!!!, feel free to comment on this..