Lace patter help

Hi all.

I am relatively new to knitting, I have only done a few small projects and am teaching myself to knit. I have never done a lace pattern and and completely confused. I read the patterns as needing more stitches than it says to cast on, and I know I am doing something wrong. this is an example…

it says to cast on multiples of 12 plus 1

row 1: (rs) P1, * ssk, k3,yo,k1,yo, k3, k2tog, p1; rep from* to end.
row 2: * k1, p11; rep from * to end

row 2 makes sense to me. row 1 is an example of when I count more than 13 sts. Idk if its the ssk, yo or k2tog that is messing me up.

You can count the sts you’ll need for the 12st repeat pattern:
The ssk takes 2sts
the yo doesn’t use a stitch, just bring the yarn forward betwen the needles and over the right needle to knit the next st
k2tog takes 2sts
and that adds up to the 12st pattern repeat. There are 2 decreases in the repeat and 2 increases (the yo’s) so you’ll end the row with the same number of sts you cast on.