1 cubic inch = .0043 gallons, or you could be more accurate .00432900433.
So Length * Width * Height * .0043 = Gallon Volume.
96*24*24 = 55296 cu/ins * .0043 = 237.77 Gallons
96*24*24* .00432900433 = 239.38
96*24*24* .00434 = 239.38
96*24*24 = 55296 cu/ins / 230 = 240.41 Gallons.
If you take, 240 Gallons and divide it by 96/24/24 you will get .004347826......
So your 230 number is the same as .004347826..... I would say that is pretty darn close. Either way will work I suppose. The Number, 231 may be more accuate.
96*24*24 / 231 = 239.376623... (Round up to 239.38, same answer as .00434)
231 = .00432900432.....(I am not sure but that is like, a bilianth of a whole number off. haha. )
I too like to do it the mathimatical way

Props for adding an equation to which many do not know.