Logging meaning

Hello
I’m new to Mikrotik, so if it seems a question of no importance to you, forgive me.
So the other day I was watching a local log server, and noticed that whenever a client disconnects, there is the following message: “[client name] logged out”, followed by some numbers, like "619 300551 373969 704 648 ". These numbers change at the end of each connection. I was just wondering, what do they mean? I googled about it but found nothing.
Thanks to anyone who can explain to me.

eMro batmoK oT meoK