due to lovibond, or a more accurate measure SRM techinically there is no need to use both 60 and 80 theroectically the 60 and 80 will produce 140 lovibond, due to each malt being klined longer or shorter due to comparision purposes, to produce a darker color, thus the number will add and not mix to a pre determine number. use 60 or 80 based on a predetermined color. not mix both in hopes to find a medium.