I see. But Hughes seems to still be a little different. Also I the formula works for @.050 lift too, which I checked with the cam specs from Comp Cams. So since Hughes only lists their timings @.050, I did a check and cam up with a duration number that does not fall in between the stated duration spec.
112 lsa + (-6÷2)×2=230. The duration spec is 216/220 for the cam. At first I thought it was the negative overplap throwing the math off, but the math checked out fine on another cam from Comp.