e.g. 168.156.27.25. This is a single IP address that demonstrates each of the 4 octets using numeric values, and separated with dots. A similar format of 168.156.027.025 that appears to be the same, is not! IP addresses use numbers, but are not actually numbers, so the leading 0's make it a different (and incorrect) IP address.

In most cases, you will want to use wildcards. Since each octect can be any number between 0 and 255, it would be very cumbersome to have to enter every IP address between 168.156.27.0 and 168.156.27.255. This full range of 0-255 can easily be represented using an asterisk as wildcard character.

A single entry of this: 168.156.27.*
is the same as entering 256 consecutive entries like this: 168.156.27.1168.156.27.2168.156.27.3...168.156.27.255.

Wildcards are very useful for representing Full Ranges, but often every value between 0 and 255 is too inclusive. Let's say that only 5 consecutive IP addresses are to be used - this is referred to as a "Partial Range" and can be represented used a hyphen (-).

A single entry of this: 168.156.27.33-38
is the same as entering 6 consecutive entries like this: 168.156.27.33 168.156.27.34 168.156.27.35 168.156.27.36 168.156.27.37 168.156.27.38.

You can use both Full and Partial Ranges in a single entry that represents hundreds, or even thousands, of individual IP Address entries.

A single entry of this: 123.55.250-255.*
is the same as entering 6 entries like this:
123.55.250.* (256 IP addresses represented with a wildcard)
123.55.251.* (256 IP addresses represented with a wildcard)
123.55.252.* (256 IP addresses represented with a wildcard)
123.55.253.* (256 IP addresses represented with a wildcard)
123.55.254.* (256 IP addresses represented with a wildcard)
123.55.255.* (256 IP addresses represented with a wildcard).

So, the single entry shown represents 1,536 individual IP Addresses (the six lines shown multiplied by the 256 IP addresses that each includes).

These addresses are reserved for specific Internet purposes and cannot be used in your IP Ranges. Refer to RFC 5735 at The Internet Engineering Task Force for technical details.