this is just another way to be able to predict genotype and phenotype ratios in dihybrid problems
this way you don't have to write the box
but it does require you to know the basic ratios that arise from monohybrids
based on the idea that: in a dihybrid, the two traits sort INDEPENDENTLY of one another i.e. what happens with one trait is completely unrelated to what happens with the other trait.
