Why is different IP address for the domain name is indicated in the control panel, while I'm not using the "additional IP" service?

This is due to the fact that we are using an additional frontend web server located at separate IP address. You need to indicate (for the domain name) the particular IP address which is given in the reference information. You may ignore the following control panel warning message: "Domain does not allow or allows another IP address. Please, change DNS settings".