How much can Nutrition Facts be off?

20%!? CeAnn, thank you for doing this research, I'm really grateful. My weight loss plan involves counting calories so this is startling. It's hard enough when I know I am going over by my own accord, but I do have a sense of trust that the numbers are correct. When I weigh my food, I do err on rounding up calories as I know portions are misleading, etc. Also, I round down when attributing calories lost by exercise (Chart says Zumba for 1/2 hour is 500 calories, I put down 300, as an example.) In the end though, I have not factored in as much as a 20% disparity. I wonder what else that 20% applies to in the world of the FDA? Ugh! Thanks, again! :)