I was reading the formula for calculating the amount of powder milk solids in the base. But I had a hard time comprehending the reason behind the lower part of the formula....see pic attached . I understand the upper part where the recommended amount of solids is subtracted with the amount of calculated solids in the serum. But then this is furthermore divided by the percentage of solids in skim milk powder minus the percentage amount of solids in liquid skim milk. ...there it gets a bit confusing. I'm guessing it's assuming that the amount of solids calculated in the upper part of the formula is not purely milk solids (without fat) so it's to get the right ratio ....but why subtract the percentage amount of solids in liquid skim milk in the Bottom half? Anyone else looked at this? Thanks