What is printing?
A printing is one manufacturing run of a volume that already has an edition. The second printing of Death Note volume 1 is the same edition as the first, and it is still a different copy.
Printings change quietly: a corrected typo, a new price, a different barcode, sometimes a different ISBN. The story and the volume number stay the same. That is why a printing is not an edition. The edition is the line. The printing is which time that volume was manufactured.
Most shelf apps stop at the series, so a reprint looks like a duplicate of a book you already own. If you collect first printings, or you bought a later printing because the first is out of stock, those are different objects. Hondana stores the printing on the volume, next to the ISBN.
You do not have to care. The field defaults to the first printing, and barcode adds fill it when the ISBN is known. It is there for the shelf where it matters.
Related
See the words on a real set in the edition catalog.