You have 3sts on the needle from the rows you've been knitting, plus 7sts picked up and 4 yarn overs. It sounds like a tab to start the shawl. You pick up also at the cast on edge so that the 7sts are picked up in the 4 slipped sts and the 3 cast on sts (the last PU3). The idea is similar to this video
except it shows picking up in the garter ridges without the yarn overs instead of picking up in the slipped sts.