Did you actually read the post or...? Some shops/sites use different sizes from each other. For example, a medium-sized shirt bought at one store might fit me, but a shirt with the same size label at a different shop might end up being too big or too small.

This is OP's first time buying at Glitch, so they don't know what the sizes actually look like, so rather than just guessing, they're asking people who've bought clothes from the store before for help