Binding off [# sts] once

[Mary Kieffer]

I am currently knitting a sweater for my granddaughter. I have reached a problem with the instructions. In shaping the armhole, the pattern reads, "bind off at arm edge [4sts] once, then [3sts] once and finally[2sts] once. I can't seem to figure out what this means and how to correctly accomplish it. It seems to mean something other than just binding off that number of individual of stitches.

Also, when the instructions read "end on WS" (or RS), should I knit the wrong side (or right side) first and then end?