What the badge is
The badge is a small printed plate on the card face reading Limited Edition with a serial number beneath it, the way numbered parallels work on retail cards. It is rendered into the card image, so it is printed as part of the artwork rather than applied afterwards.
Adding one
From a finished card in your box, open Add Badge. Set the size, drag or choose the position, pick a style, and set the edition size. The card preview updates so you can see how it sits against the design before you order.
How numbering works on copies
When a badged design is printed in copies, the copies count up in sequence, 1 of N through N of N, across the whole order. The N is measured from the number of copies actually ordered, so a badge set for 25 on a run of 25 prints 1/25 through 25/25.
A design that exists once prints as a single numbered card. That is the custom equivalent of a 1-of-1.
Tips
Place the badge where it does not cover a face or the name plate; corners usually work. Keep the badge size modest so it reads as a mark rather than a sticker. And decide on the edition size before ordering, because the numbers print with the cards and cannot be changed afterwards.