...
Enter the name of the new Realm..
Click OK, but then right-click and edit the new Realm
You will see that a virtual host IP address has been assigned. If you wish to modify this address this can only be done via the CLI. Please refer to the guide FortinetDocument library... https://docs.fortinet.com/document/fortiproxy/7.2.1/cli-reference/200620/config-vpn-ssl-web-realm
...