I love PB&J and used to buy uncrustables, the problem is they are small, and it takes about 2 bites to finish one, it’s easy to eat the entire box at one time, which is why I stopped buying them.
It was like Girl Scout Cookies, one sleeve equals one serving if you are not careful, especially with a cold glass of milk to go with them.
I saw a posting on Facebook about one-pound bacon packages that applies here - if the package is not re-sealable, then Science says that is a single serving!
How are you when you are left alone with a box of Cheez-its