The 1st digit of the UPC code indicates it's use. The 1st digit of "3" is reserved for drugs and pharmaceuticals and indicates that the number that follows is it's National Drug Code (which, is probably what the "N" means). I believe that UPC-B is specifically for the National Drug Code stuff, so, I'll bet if you print it under UPC-B, the "N" will print as a constant, but, not as part of the actual bar code