When I worked for a cafeteria-style restaurant chain, I had to measure out all the items in master recipes. One thing I had to learn was what we called "clean weight", the equivalent of net weight. If a recipe called for 10 pounds of onions, for instance, I'd have to weigh out 12 pounds of onions to account for the outer layers the cooks couldn't use. It would be the same for other foods, like the weight of fruit peels or the amount of fat on a cut of meat. The recipe called for clean weight or net weight, not the actual weight straight out of the container.
At closing time, I'd have to weigh all of the unsold food items and record that weight on a credit sheet. I had to know all of the tare weights of the pans and containers the cooks brought back, so I could subtract it from the actual net weight of the food. One kind of flat pan weighed 2 pounds, for instance, so if a leftover piece of roast beef weighed 14 pounds on the scale, I'd record it as 12 pounds on the credit sheet.