bontesel White Engagement Dress Promise Dress Wedding Dress

I can't say anything about the quality and sewing of the product, but in the seller's questions, the answer was written that someone who gives a waist measurement of 78 and a chest measurement of 96 should be told a size 40. Therefore, I ordered size 40 to be comfortable. We are paying this much money, the waist measurement of the dress that arrives is 68 cm, if you force it, it becomes 70 cm. It says size L on the tag. I will return it, but I am faced with the problem of which size should I tell. It shouldn't be too hard to put a sizing guide up there.