Pistons specs question for 340 build

I have calculated the combustion space around the top of the piston down to the first ring. I get somewhere between .5 and .6 cc. It could be double that with a kb hyper. I dont think that is hugely significant. But i agree, someone thinks they have a 12cc dome, and its really 7, or thinks the have a 10cc dish, and its really 23........?