You are right it starts with CO 9 and the first row is:
Row 1 (right side): Slip (sl) 1, p2, yo, sl 1, k1, pass slip stitch over (psso), yo, sl 1, k1, psso, yo, k2 – 10 stitches (yarn over counts as a stitch.
This only uses 9 stitches but ends up being 10 when you finish the row. I noticed the stitch count changed over the course of the pattern stitch increasing and then going back to 9 to start over.
Here is how row 1 works: Slip 1 stitch, p2, (3 sts so far), yarn over (which doesn’t involve any stitches), slip 1, k1 pass slipped stitch over, (that last part was another 2 stitches, so we’re up to 5 now), yarn over (no stitches), slip 1, k1, psso (another 2 stitches so we are now up to 7), k2. That uses a total of 9, but you end up with 10 sts because you have 3 yarn overs and only 2 decreased stitches (the sl1, k1, psso that you do twiced).
I wonder if you have understood a yarn over to involve working the next stitch. It doesn’t. The yarn over is done completely between stitches— the part you do that makes the extra strand over the needle that will make a hole when you work it in the next row. I’m sure there must be videos about yarn overs on this site. You need to do two different kinds of yo here because one time the yo is after a purl st with the sl, k1, psso next and another two are basically between knits with some fanciness thrown in.