The measurements that appear next to the sizes of the products correspond to the length and width of the garments, that is, if the size "S" indicates "length 70 cm x width 48 cm", this means that the garment has a length of 70 cm and a width of 48 cm.
With these measurements, the easiest way not to be mistaken when selecting the size is by measuring a similar garment from the ones you already have in the store and selecting, for these measurements, the units and sizes you want.
Remember that the garments are always the same for all brands, so the sizes will not vary by brands but depending on the type of garment.