Yes. To clarify, the number in CIDR notation is the number of bits in the subnet mask. For example, a /24 indicates a subnet mask of 24 bits; that is:
11111111.11111111.11111111.00000000
Which is to say:
255.255.255.0
Which is to say that the first three octets are taken to indicate the network ID, and the last octet may vary to indicate different hosts. It's a short way of saying "This subnet encompasses x.x.x.0 through x.x.x.255".
Here's a useful chart for seeing how many hosts will be blocked by a range ban using CIDR notation, so you can make sure you aren't banning unreasonably large ranges: http://bradthemad.org/tech/notes/cidr_subnets.php
11111111.11111111.11111111.00000000
Which is to say:
255.255.255.0
Which is to say that the first three octets are taken to indicate the network ID, and the last octet may vary to indicate different hosts. It's a short way of saying "This subnet encompasses x.x.x.0 through x.x.x.255".
Here's a useful chart for seeing how many hosts will be blocked by a range ban using CIDR notation, so you can make sure you aren't banning unreasonably large ranges: http://bradthemad.org/tech/notes/cidr_subnets.php