UpdateSession doesn't reduce number of players (NumOpenPublicConnections). C++

I call UpdateSession in PostLogin and Logout to refresh the session stats but when a player leaves the number (NumOpenPublicConnections) doesn’t change? It seems to go up when players join though, any idea why?

This is with OnlineSubsystemSteam (not SteamSockets). Listen servers. UE4.27. Internet sessions.

Thanks.