Hi lots of lotions,
Thanks for posting your question here. I just reviewed the "UPC" field on our lister page and confirmed that it currently supports the entry of up to 12 digits. Given that standard UPC codes contain 12 digits, I am not certain what may be causing your codes to come out missing one number as you have described.
However, based on the specific behavior you described, I am curious if you may be entering some other type of code, such as an EAN-13, which contains 13 digits.
If you continue to have trouble with this, please contact our Customer Support team directly from under the “Help” tab within your account and we will be happy to continue working with you. I'm sure we will be able to figure things out once we have reviewed a couple examples of this behavior.
-Mike