Why were two 0's added to the end of a String column?

I have a column that stores many codes, I can run my bot until a certain point where I then receive this error:


I understand it is because of the input string 9027809900 although in my Excel file this string does not exist. The column looks as so:


I do not understand where the additional 0 characters are coming from and stopping my bot from running. Any ideas?