From what I can tell, the number is 4. But I don't know if the level of the warning makes any difference. I don't think so, because llmmzz's final warning was the mildest level, and it was still enough to trigger the auto-ban feature.
I can't tell for sure. It looks like it might be possible that it's only a two-week ban. But it might also just be that the warning was the type that would have jailed for two weeks. It's not really clear. I guess we'll find out in two weeks!