All measurements in these size charts are in inches and actual garment measurements, when the garment is in its relaxed state. The measurements do not account for stretch or other garment features. A short laying flat on the table will have these exact waist measurements. To find a size that suits you you can measure yourself and then account for the stretch or you can use another garment which has the fit you require. Simply match these measurements to the size chart. If you are between sizes go with the smaller size for a tighter fit or go with the larger size for a more loose fit.
Every garment has a different type of fit (loose, regular, fitted, compression). This is mentioned on the product page under “Techical Info”.