Oh, YOU don't mind if it's full. Well, what a relief! I'm glad to know that YOU don't mind cleaning up after people, covering the extra for pizza, having people over who don't pay (and thus wouldn't be practicing at an arcade anyway, coughcough), and waiting an hour between games. If my opinion is irrelevant, why bother asking before you show up? I just live here, after all. I'm sure YOU wouldn't mind if I was asleep or busy or dead, as long as there's "people that you find the game enjoying".
One more like that and you're not invited again, ever. And you most certainly are not welcome today.
I don't like telling people they can't come, especially if I already said yes, but more than ten people is incredibly excessive for this size room, and I will give people their first shot at playing CS over someone that's been here a few times, since it's fairer (to me).