[@Winter Star12]

So, if you notice there are a list of roles that are there, each role has a number associated with them. These are the numbers that it is referring to. No character knows who they are, or what their background is, but each one has a tattoo of their number on their arm, and so this is the number that they go by. Once they discover their actual names, they have the option of going by that or continue using the number.

Does this answer your question?