Need advice from experienced Windsor builder

[jwshira]

Just replaced my harmonic damper because the old one had gotten antifreeze dripped on it during life with the P.O., and was impossible to read the markings.
I decided to check to see that TDC on the damper (zero degrees) lined up correctly with the timing tab when the number one piston was at TDC.
Put a piston stop in #1, and ran it around both directions. Yes, checked to make sure I was on compression stroke, just because.
I found that when I hit the stop when going in normal crank rotation direction, it stopped at 4 degrees before the zero degree mark. (4 degrees BTDC)
Spun it the other way, and it stopped at 12 degrees before the zero mark. (12 degrees ATDC)
16 degrees total difference between the two marks.
To me, this tells me that I would turn the crank in its normal rotation direction for 8 more degrees, and I'd be at true TDC. (I know there's some slop, but I'm not going to pull the head to check it the "right way."

If I do that, the timing tab is going to be sitting at a point 4 degrees on the ATDC side of zero.

Here's where I'm confusing myself:
In a perfect world, I'd move the timing tab so that after I rotated that extra 8 degrees, it lined up on the zero mark.
I think that means I'd move the tab 4 degrees clockwise, viewed from the front of the motor.
Can anyone confirm that I'm on the right track? (or not)

But...even if I am right, the timing tab can't be adjusted. It's bolted firmly to the block with no provision to change its location.

So...how do I deal with that?

Do I just do the mental math when I put a timing light on it and make an allowance for the "missing" 4 degrees?

Sorry for the length of this, but it's driving me buggy and I hope someone out there can clear this up for me.