Help with Chain Stitch Rib

Goodness, I haven’t posted in a while! Anyway, I am knitting a scarf for a friend and trying to use the chain stitch rib. I am unsure however of what exactly I am supposed to do in the last row. Here is the stitch pattern:

multiple of 3+2
row 1: k2,p1, k2; rep from to end.
row 2: p2,k1, p2; rep from to end.
row 3: as row 1.
row 4: p2, yb, insert needle through centre of st 3 rows below next st on needle and knit this in the usual way, slipping st above off needle at the same time, p2; rep from to end.

Thanks for your help!

Row 4 - p 2, then with the yarn in back, put the needle in the st that’s 3 sts below the next st on the left needle and knit it, slipping all sts off the left needle (that’s the one on the needle, the one below it and the one below it), then repeat, ending with p2. Don’t try to figure it out in your head, grab some needles and scrap yarn and CO about 14 or 17 sts and try it out. Also, click on the Glossary and look for k-b for a video in how to knit in the st below. It shows going down only one row, you’re going to go down to the 3rd row.

Ahhh! After watching the video several times, it makes perfect sense. I was thinking a literal stitch which didn’t make sense at all. Thanks!