So you question really is, in the published expression: AT x mS x C / AR x mT x 60.8 x 100, where the 60.8 comes from? That's sort of a fudge factor this sort of compendium use when they simplify the procedure for you. You can certainly try to figure out how they got the fudge factor, if you feel the need (and have the time,) to learn more. What does each factor stand for? How do they all relate? Do you recognize 60.8 -- is that a MW, or something like that?