No, that's not correct.

The tutorial referenced is for a hot-masternode, local configuration, which would only have one ip address.

Each masternode needs its own ip address, so you're limited to one /for that setup/.

If you want to set up two masternodes, your second one will have to be on another ip address.

You can either setup your own remote vps instance:

https://status.bolehvpn.net/2016/02/07/what-is-a-dash-masternode-and-how-do-i-set-up-one/
https://www.dash.org/forum/threads/taos-masternode-setup-guide-for-dummies-updated.2680/

Or pay a masternode provider to do it for you:

https://masternode.me/
https://node40.com/
more: https://dashpay.atlassian.net/wiki/pages/viewpage.action?pageId=1867885

HTH