The pattern tells me: " The marker is the beginning of the round, and from this point, keep the edes of your hat in garter stitch, which means purling the stitches on the garter edges on this round. You want 2 garter ridges on the front and back of the hat"
I tried just purling each row when I got to this part of the hat. It doesn't give me any ridges on the back side. It looks like stockinette. (which, now that I think about, makes sense on circular needles!
I think I just answered my own question, but replies are welcome!