There are no official numerical user ID's on bluesky. Everyone has a unique, persistent Decentralized Identifier (DID) that usually looks something like "did:plc:ewvi7nxzyoun6zhxrhs64oiz". Checking for new DID's on the various PDS servers of the platform is done continuously, and once they are found, they are assigned a numerical ID. There is no guarantee that this always works well, so please regard these twexID's as best efforts to give you a sense of how many accounts were registered on Bluesky.