Many people like to configure reverse DNS for their virtual machine IP address(es). This is often done for several reasons, with the main purpose generally being white-labelling.
To do this:
You should then see the IP address, subnet mask, default gateway, and hostname for the virtual machine, the latter of which can be changed.
To configure reverse DNS, the hostname you intend to use must be set to point to the VPS beforehand.
For example, if the IP address you were doing this for was 188.8.131.52, and you wanted to use 20isupport.com as the hostname, you would point the non-www A record for 20isupport.com to 184.108.40.206. This process would be the same for any hostname you wish to use.
Once you have the appropriate A record in place, select Edit under Hostname.
Enter the hostname you want to use - which should have been configured to point to the IP address you’re doing this for beforehand - and Save.