What customers see behind the “Size guide” link. One chart can serve many products — a plain and a printed tee cut from the same blank share measurements.
Check the numbers against a real garment before publishing. The chart the storefront shipped with was invented, and size/fit is already the biggest reason stock comes back (see Margins). Whether you upload your supplier's chart or type one in, measure one tee flat and confirm it matches — a wrong chart is a return you pay for.