Numerical value in cell keeps getting changed when I click away from it

I have a spreadsheet where it is entirely just manually input data (it is a personal inventory of books and comics). There are no formulas in the entire document. The only thing I have on some columns is conditional formatting to fill empty cells with red.

The problem I have is on the column where I input the isbn numbers of books and barcode numbers of comics. The isbn numbers I don't have a problem with, but for some reason I have an issue with the comic barcode numbers. The column had initially been set to a number data format, but the dashes in isbn numbers has caused the cells with isbn numbers to be set to the automatic data format. That's fine. I understand why that happened. The cells with the barcode numbers for comics is still set to the number data format. For some reason, after typing in the 17 digit barcode number, Numbers is changing the last two digits to zeroes as soon as I move out of the cell.

I can't for the life of me figure out why this is happening. There are no formulas, decimals, only one conditional formatting rule for blank cells. It isn't a date or time where numbers might change how it looks. It doesn't happen when I set the data format to text, but I'd like to figure out why this is happening on the number data format.

Here is an example of one of the barcode numbers: 76194137651600431. As soon as I move to a different cell, it gets automatically changed to 76194137651600400.