you could check the different rules. In some way the basic rule is like chinese: you count all (emptyness and boundaries) So captured stones really dont matter and will be simply put away from the board back in the bowls.
In the japanese rule, we count only emptyness. How can we do that? Well we can assume that we play same quantity of stones as we alternate. So if we keep track of prisoners by putting them back on the board, we should get same result as in chinese rule.
Note: its almost true to 1 point difference due to the fact of who will end the game, and it gives other sets of rules (AGA, french...) to make both rules equivalent