This is the address of the subnet in Internet Protocol version 4 (IPv4) format of the area to which the rule will apply in ...

This is the address of the subnet in Internet Protocol version 4 (IPv4) format of the area to which the rule will apply in the case of a reverse lookup. For example, in the example 1.2.3.4/16, the subnet in a reverse lookup is 1.2.3.4 and /16 is the prefix.