Be sure you are not confusing yourself with degrees, IE your timing tape probably goes right from 0 around to 360. So bear in mind that the degree figures CHANGE in their reference, that is:
Intake shown opens at 34 BTC
closes at 66 ABDC
Exhaust shown closes at 30 ATDC
opens at 78 BBDC
So on your 0-360 tape, you have to figure these depending on how the tape is marked. If BDC is marked 180, then you'd have to add 180 to the 66* ABDC figure, etc