It's explaining to you how to do a knit cast on. You would put the needle with the working yarn into your left hand by turning as if you were at the end of the row. Then knit into the first stitch, leave it and put the new stitch on the same needle. I'm getting 30 sts too. Unless, after the last k3, you just purl the remaining stiches..? That's probably it.
sue- knitting heretic