Some people are obsessed with exact measurements of foods. I know that every cow did not eat the same grass or walk the same distance to the barn. Each bean plant didn't get the same amount of sun or water. Labels aren't always correct. Do your best, but nutrition values are estimates at best.
It is good to be as accurate as you can when entering food values, but don't obsess. You're not going to get it exactly right no matter how hard you try.