The mark is a reference point .
Depending on what your after or how you want to set the timing .
Most use static , so at an idle or roll over speed if using a starter .
Now if you want 34* at 6000 rpm its a little more complicated .
You want it at (or near) peak torque ~4000 rpm on a stocker. That's where ignition timing is most critical.
The mark itself is just a reference. The actual firing point is as the trailing edge of the magnet is directly under the right hand most edge of the D shaped pick-up module (located under the coil body.) Most builders will simply place their chalk mark on the flywheel at the right coil leg for easier visibility.