Problem understanding bind-off instructions
I'm making the front left side of a shrug, and as per the instructions, I knitted it to 8 inches. There are 30 stitches on the needle. It's time to shape the armhole, and this is what the instructions read: "At armhole edge, BO 3 sts once, then BO 2 sts once. 25 sts rem."
What's up with that? Does anyone know why I can't just bind off five stitches? There's got to be a reason it's written that way, but I can't figure it out, and Google isn't helping.