OK you will need to do a couple of things on the barcode object then. First up go into barcode options and set the barcode type to UPC-A.
Next you will need to pad your 8 digit number as it needs to be 11 digits long (a 12th digit will be automatically calculated as a checksum). So, we just need to add 3 leading zeroes to the front of our data selection. In your case, go to the 'Data' setting, tick the box labelled 'Custom Data selection' and shove this in the box:
='000'+@(&Current.Line,114,121)
That ought to work