One in every generation - once she dies, the next one's called. There's two right now, though. It's complicated.

[It's probably more than he needs, the explanation that Buffy died - briefly, technically - so another Slayer was called, that one was killed, and then the torch passed to Faith. Meanwhile, Buffy is still alive and well and fighting the good fight.]

I... probably wouldn't try to fight Faith if I were you.

[Well, actually. She's not at all surprised that that is exactly what Savage wants to do, but she doesn't want to see either of them get hurt.]