I haven't long got up, but surely that is 1 part to three, which is the same as saying 25% plus 75% to make 100%? I think the devil is in the detail... what do the instructions ACTUALLY say?
1 to 4 so there's 5 parts in total. So divide how much you want by 5, then times that answer by 1 to get the first quantity and times the answer by 4 to get the second quantity.