Or you are assuming something that, while commonly occurring and so fairly reasonable to presume, isn't occurring in my particular case. You can look the values up yourself, so the only viable reason is that the food producers are lying on their packaging.
Yes I am making an assumption, my assumption is that you’re not some magical being and the laws of physics still apply to you as they do to everyone else. It’s a pretty reasonable assumption to make.
Food producers lying on their labels is unlikely to be the explanation here - the source of error here is likely just you.