It sounds like they want you to purl 2 together through the back loop (P2tog-tbl). Click over on the Glossary tab, then scroll down to the P's. There's a video there how to do it. It can be an awkward stitch to preform.
Mirl56 at Ravelry, too.
Learn from the mistakes of others. You canít live long enough to make them all yourself. Eleanor Roosevelt
Lady Feb Sweater
more shawlettes, socks