Question about stabbing a distributor

[Ohio Ken]

Hello
I would like your input on this subject
1st let's say you had a totally stock 351w (mine is not but for sake of a baseline)
It would call for base idle timing of 10 degrees btdc.
I have read many threads that if you are installing a distributor you would stab it at 0 degree tdc, where as others say you would want to stab it at 10 degrees btdc. It makes sense that stabbing at 10 degrees btdc would make it easier to start the car before fine tuning with a timing light.
However, the part that confuses me is as follows:

If you stab at 0 degrees tdc and rotor is to point to #1 terminal, it would make sense that you would then advance to the 10 degree mark under a timing light.

However, if you stab it at 10 degrees btdc and also point the rotor to the #1 terminal, would this not show as 20 degrees btdc using the light?

The reason I ask, is I did stab mine at 10 degrees btdc, but under the light it shows 20 degrees. If I turn the dizzy to 10 degrees under the light, the engine runs way retarded, and runs very hot, and hard to turn over when hot, and when cold turns over fine but doesn't want to fire.

The way I figure it, if you stab it at any degree advance of 0 degrees, the timing light would not read accurate against the timing slashes on the balancer..

Edited: I was wrong in my assumption, it turns out that the extra 10* was coming from my mechanical advance, thus giving me 20* initial and 34*!at 3000rmp, thanks to all for sharing your knowledge!
Thanks Ken