Formal, full length, strapless, chiffon dress

Elegant, flattering, strapless gown. Fully lined, black chiffon. Bust area has flattering fabric gather. Chiffon tie in back. Back Zipper. Flattering Ruching at waist. Worn once, to an evening wedding. The size on the dress says it’s a size 10, but purchased at a bridal boutique...and it’s more like a 6. Maybe bridal stuff is sized differently than regular dresses? I’m 5’5” tall and wear a 4-6. Jeans 27-28. I can give exact dress measurements if interested.