Timing belt change - marks on flywheel and on vibration damper not aligning

[Radek]

Here's another puzzle with my son's 1988 90Q.  We are doing the timing belt, everything works fine and according to Bentley, except that when the crankshaft is set to mark "0" on the flywheel, the notch on the front vibration damper is behind by 10-15 degrees.    When moving the crankshaft to the vibration damper notch, there is nothing visible on the flywheel at all.

I removed the #1 spark plug and put in a stick.  Clearly, the top coincides with the flywheel mark.   I'm planning to go with the flywheel mark for the purposes of aligning the camshaft, since clearly the piston is at TDC then.  I checked the part number of the vibration damper thinking it could be from a different model, but it is a correct one.  Is there a logical explanation? Am I doing anything wrong?  Rotating the engine clockwise, standing in front facing the car.
I hope the collective wisdom of the group can explain this puzzle.  Thanks.

Radek.