I think the size chart is wrong. My waist size is 34 and I bought an L size (32 on the product size chart). It was a little loose and didn't show any reduction my tummy shape. But It shows my tummy shapes as it is. The L size shapewear is suitable for 40 waist sized people.
Note: When you buy shapewear Buy one size lesser. (Eg : if your waist size is 34, then buy 30 size)