Hot Rods Timing & Advance question SBC w/HEI

Actually, No. At 3K RPM you'll see the total of your initial (12-15deg) + your mechanical (28deg) so if you have initial at 12deg and mechanical of another 28eg then you'll have a total of 40degrees. The mechanical is how much more the distributor will contribute to your initial (or starting point) timing.
I think other posters are advising you to have a total of 36 or 38degrees, lets say 36 degrees, so your mechanical is 28 - the 36 you want so your initial is 8 degrees. I'd feel comfortable with 36 degrees puttin around on the street myself.