Your timing tab should have numbers for -0-, -4-, -8-, -12- on the upper side, or BTDC. I believe every mark on the timing tab is 2° and ever peak of the saw-tooth point is 4° apart.
Alternatively, you could use a dial-back timing light or put a timing tape on your balancer.
Depending on the condition of your harmonic balancer your TDC mark may or may not be accurate.