Serial numbering is supposed to make each copy of a card unique. They’re also a way of confirming a card’s overall quantity. Twenty cards in 2022 Bowman Draft Baseball have an error with four of their parallels. Instead of each serial number being different, all of them are the same.
If you have a Purple Jace Jung #BD-15, it’ll be numbered 152/250. All 250 copies are. Every Sky Blue Brady House #BD-144 has a 251/499 serial number. All Aqua Jordan Walker cards are 087/199.