From what I've been able to find these seem to be the most common interpretations:

12 plants total, 6 in flowering and 12 in veg

18 plants total, 6 in the flowering cycle and 12 in the veg cycle

Looks like either one of these would be safe, since there doesn't seem to be a court case i can find to set a precedent for which is the answer. If you live in an area that's ok with mmj the police seem to just kill the plants they think is over the limit and not press charges.