The options on this page effect the master PPTP server process, which accepts network connections from clients and then starts a PPP daemon to handle them. The most important are the IP addresses for the client and server ends of the connection. The server address can be set to a single IP (like 192.168.1.1), but the client addresses should be a range or ranges big enough to handle all the simultanous clients that you expect (such as 192.168.1.100-200).