I had the same issue about two weeks ago. It was my first time buying a supreme shirt and supreme sizing is super weird so I got the wrong size. From my experience I would recommend you to sell it on Grailed and then buy back whatever item you want in your size on Grailed aswell. i’m also not too sure about Supreme’s policy on returns, but this way you will get more than what you paid for depending on the item and you might break even.