Divide front from back?

I am making the perfect periwinkle turtleneck vest and I an done with the ribbing of the neck then it says:

[b]divide the front from back. it says bind off 9 sts, rib 12 knit 21 rib 12, BO 9, rib 12, k21, rib 12

then it says 45 stitches each half (all sizes)

when it says rib 12, what does that mean?[/b]

Thanks!

nevermind. i got it :cheering: :cheering:

Great!