You need to hit the stop in both the CW and CCW directions in order to compute True TDC. Both are mentioned above.

Here is a step by step example with numbers:

1. Rough eyeball TDC before adding stop.

2. Move degree wheel/pointer to zero and lock down on balancer.

3. Rotate crank roughly 20* CW and install stop, making sure the bolt just touches the top of the piston.

4. Rotate crank 300+* CW (Yes CW again)

*until you hit the stop.* Lets say it stops at 338*. This is your first real measurement so write it down.

5. Next rotate crank CCW

*until it hits the stop.* Lets say that it now reads 16*. Write it down as your 2nd measurement location. From these two values you can now calculate True TDC.

6. First subtract 338 from 360 (TDC= 0/360), which gives you 22*. This gives you the value from TDC that you found when going CW.

7. Add that value to the value that you found when going CCW. 22+16=38.

8. Now take the 38 that you just computed and divide by 2, which gives 19.

9. Subtract that from the value that you found when rotating CCW. 16 -19 =-3. Since it is a neqative #, you will need to subtract that 3 from 360. That will equate to 357* on your degree wheel.

10. 357* is where True TDC is currently found on your degree wheel.

*At that point the piston will be at its highest point in the bore.*

11. Remove stop and rotate crank to 357*.

12. Carefully loosen degree wheel from crank and rotate the wheel to "0" and lock it down.

*You now have the motor and degree wheel both aligned to TDC.*

Truth be told, you can also use your dial indicator method to find TDC if you want to and work with that. It will not be as accurate as to what I am trying to portray to you, but unless you are using an infinitely adjustable timing set like this (which lets you set the cam timing up perfectly):

https://www.summitracing.com/parts/clo-9-3735Specifically note the slots (under the 6 bolts) that allow adjustment on the upper cam gear.

If you are using the simpler multi key version without the slots, you will at least be in the ball park.