Summer maxi dress tag says Dior (most likely not authentic)

Summer maxi dress tag says Dior not sure if it’s authentic. Most likely it’s NOT Size: 4 ( it fits like a medium / large) Has stretch towards the chest area on the back of the dress. Chest 19.5 (stretched out) Waist 14 (has no stretch on the waist) Length 46 (from the pit)