Finish a number you already own. Then Generate puts the barcode on a label.
Paste the digits you already own. This does not issue a UPC.
Retail barcodes end with a check digit so a mis-scan fails instead of ringing up the wrong SKU. Paste the digits you have. This calculator does not issue GTIN or UPC numbers. It only computes the last digit using the standard modulo-10 method.
No. You need numbers from GS1 or a prefix you already own. This only finishes the check digit on digits you paste.