Timing Mark Question

Ok before I ask I must say I searched, I looked at the FSM, and I asked other people. Anyway I have an 87 turbo Z and I want to check the timing. I'm sure it is ok but when I looked to make sure with the timing light, I seen something confusing. The marks on the crank pully whet like | | | 0 0 0 0 0 | | | | | | | . The fsm showed seven lines and a lot of space before the circles. I know I'm suppose to be at 20* but what in that is 20*? Also I see alot of people advancing timing what is the most I can advance on a stock set up with front mount and 11-12psi? thanks