Well if we run through it we have:
Overhead Left and Right
A microphone for each of the toms
2 microphones to each snare drum in order to get both the drum and snare sound.
A microphone to the hi-hat
A microphone to the ride cymbal to bring out it's definition
2 microphones to the bass drum. One captures the overall sound and another the attack.
So there we have our 13.
ideally I would have placed two microphones at the far end of the room in order to get a nice natural reverbish noise, but I didn't have enough stands.