First, I’ll tell you what it DOESN’T mean… It doesn’t mean that only 1% of the calories come from fat.
Here’s what it DOES mean: That 99% of the weight of the food is fat-free. So if the food weighs 100 grams, 1 gram comes from fat. And every gram of fat contains 9 calories. So depending on how much a food weighs, it may contain more fat than you expect.