Bobi Los Angeles Ribbed Square Neckline Sweater

Bobi Los Angeles ribbed sweater new with tags size XS in a wine color. Has stretch. It has a darkened spot on the fabric at the back bottom near the side seam. Looks bigger in the photo, measures about 1”. I dont know if it’s manufacturer flaw or something that can be removed. Priced accordingly Bust not stretched 14” across Length 23”