They tell you to bind off in steps so you have a gradual change in your knitting rather than an abrupt one.
If all the binding off is at the neck edge, always do it at the beginning of the row, otherwise your yarn will be in the wrong place. So bind of the first 4, work to the end of the row, purl back (assuming the wrong side is purl). then bind off the second 4, work to the end, purl back, then bind of 2, then 2, the same way, then I assume 16 are the rest.
I've found, hence my little motto at the bottom, is that it's usually best just to do what the pattern says. Occasionally there is a mistake, but usually if you just do what they say, you understand why afterwards.