While in the Master zone your hostname is pointed to an IP address, using the Master Reverse zone allows you to point an IP address to a hostname.
The PTR record has the following look in your ClouDNS Control Panel:
How to add it?
Go to the Control Panel of your Master Reverse Zone and click on "Add new record". Type, as follow:
For IP subnetwork 127.0.0 with Master Reverse Zone 0.0.127.in-addr.arpa
and so on.
After creating the PTR record, you need to ask the IP owner to delegate the management of the IP to our servers.