I got to thinking... you might be misinterpreting it. The kpk is done in one stitch, the p3tog is over the next 3 sts. Those are repeated 3 times. So they use up 4 sts, times 3 is 12 and a k2 after them for 14 and you repeat all of it again. That gives you 28 sts, plus the 2 at the beg and 1 at the end for 31. So the numbers work out.
sue- knitting heretic