I buy 52 slots!
But I set the number at 50 in server at "serverhostsettings.json"'s MaxConnectedUsers,
but when I turn on the server , the max number is still 40,
and the few minutes afterwards "MaxConnectedUsers" change the setting to 40 automatically.
the situation stays the same when I delete the "serverhostsettings.json" file.
It's been five days and no one wants to fix it.