4+6=12?!?!
3 leads (limb leads) I, II, III
6 Vector leads - V1-V6
3 Augmented voltage (aV) leads - aVR(right), aVL(left), and aVF(foot).
3+3+6=12 views
the green RL (right leg) lead is there for the aug leads, these leads are a summation of the other leads, and essentially form a set...