I expect that we in the U.S. are not so very different, and that there are quite a few cutters here in the same boat, although they may not acknowledge it to anyone. In seems that quite a few people, including college graduates, do not understand ratios, even though they run into them every time they pay the sales tax on items they purchase.
Percent means per hundred.
In money the dollar is the basic unit, to which all other amounts are compared. If you have learned to hate math in school, or find that abstract symbols like L, W, X, Y are slippery, then bear with me. For cutting stones there are only a few such symbols, and they occur over and over. If you can learn them, they can furnish you with a lot of information you would otherwise be missing. On faceted stones and diagrams for them, the width is the basic unit to which all other measurements are compared.