Pertronix and Timing ?

[hoosierdaddy]

I just installed my pertronix ignition and I wanted to thank Pelican for the search function so I could get proper instructions on installation . My second question , when setting the timing I noticed there were three notch's in my crank pulley can anyone explain why there are three . I'm not 100% sure I have the timing set right but I do know the car runs fantastic . I'm meeting my brother in the late spring or early summer probably in the southeast so I can chase him around for a week in his new 350z track version , so I'm starting early to get my car right .

Jim