Not knowing the rest of the pattern, I'd assume that for the next 13 stitches, you'll knit on one row and when you get back to that group of 13 stitches on the next row, you'll purl them.
What are you making?
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