I think they probably just did it for overall packaging clarification. It says "collect all 24" and then if you count there is only 21 without looking at the silhouettes so I'm guessing they just did the sticker to fix that. The same sticker is on the back of the foil package and printing a single color sticker to put over the 2 places was most likely just cheaper than reprinting full color foil packages and brochures.