The charts are for various collections.Not every size is available in every collection.
These measurements are general measurements for all styles in a collection. The vendor size chart is provided as an aid in selecting the proper size.
Measure carefully as the charts are helpful but not always perfect. They are approximate (in inches) just to show the differences between sizes.
All styles fit differently depending on fabric and style. A-line type dresses will be bigger than size chart. No waistline dress – The waist will be bigger than chart.
You should have someone measure you in your under garment.
Your seamstress is the ideal person as most dresses will need some alterations for a perfect fit.
Two photos (Front & Profile) would be most helpful in determining the appropriate size. You should order the size based on the LARGEST measurement on the chart.
If you are in between sizes on the chart, you should order the larger size. It is much easier to take in a dress than it is to make it larger.