Confused dividing for left back (cute angel top)

[amanda598]

Hello! Never posted on here before so here goes nothing... :P

So i'm currently knitting an 'Angel Top' for a little bubba soon to be in our family and i've done the lace pattern of the bottom of the cardigan and now i have to 'divide for left back'. It says this:

Break off M. Use C for next 6 rows.
1st row: cast on and knit 2 sts k1 (k1 yn fwd k3 sl 1 k2 psso etc etc) 3 times k3 k2 tog and work on these 37 stitches.

How on earth do i know how many to cast on?! Or does it mean that the knit 2 sts k1 (k1 yn fwd k3 sl 1 k2 psso etc etc) 3 times k3 k2 tog is the 'cast on'?

ANY help would be extremely gratefully received :-)