The split measurement isn't an exact one, sometimes there are other things to take into account,and oftentimes no two kiltmakers will come up with exactly the same numbers.
It's often something that comes with experience, when I start the sums, I often compromise to make the sewing of the pleats a little easier, sometimes the size or number of the pleats determines the final calculations.
So rest assured there is no absolute "right" answer, just some that work better than others!