Answer: I am not sure if I remember but I believe if the single digit matches the last digit on the barcode then the barcode is correct or valid.
But, If the digit is different from the one on your computer then their is an error. I recommend In order to check for error is to remove the received check digit and recalculate it based on the 12-digit identification code. (This I use for EAN-13 but since Ean-8 is basically short version of 13 try it)