if you run a host using the LFS Client, you can have 24 slots, but one is always taken up by the client thats hosting, while on a dedi, you can have 23 slots, but the dedi doesn't take up a slot
It's not a bug.
It's a non-dedicated server and the 24th player is the host.
On dedicated servers the host takes up one slot and that leaves 23 slots for players.