The increase or decrease is done so that you have a # that is to be divisible for the way in which you decrease. For example, in the formula I gave you the decreasing is begun with multiples of 10 (k2tog, k8=10 sts). The increase/decrease is done to accomodate the decreasing for the crown of the hat, if the cast on # is a number that you can use for the crown decrease (multiples of x), then you don't need to increase or decrease when you begin stockinette because you have the correct amt of sts for the crown decrease...does this make sense?
