I made the assumtion that you would slip off the stitch, doesn't seem to be the case.
The first row: Sl1k, then *k2tog, yo twice, sl, k1, psso then repeat from the *
The second row: sl1k, * k2, p1, k1, repeat from *
It looks like you're slipping the first stitch of each row for a selvedge, just a way to make the edge look smooth.
I'm sorry if I messed you up, but my guess about dropping that extra yo was wrong. :oops: