Pearl Pink Sleeveless Vest by Susan Robicheau

Pearl Pink Sleeveless Vest

Knitting
Bulky (7 wpi) ?
14 stitches and 20 rows = 4 inches
in Patterned Rib
US 9 - 5.5 mm
US 10 - 6.0 mm
600 - 1680 yards (549 - 1536 m)
Small, Medium, Large X-Large, 2X-Large, 3X-Large
English
Errata available: crochetmagazine.com

What does “Place marker on each side of center” mean? I am confused. I am making the small size. The center is 34 sts. So what is meant by the “36 sts”?