jew media mentions this: https://encyclopedia.ushmm.org/content/en/article/tattoos-and-numbers-the-system-of-identifying-prisoners-at-auschwitz anyone in a camp had a number, usually sewn onto their uniform, Auschwitz jews later had a tattoo instead. There's not a massive discrepancy between the numbers killed and the numbering system. They later added an A or B prefix to stop it getting too long.