%BOperServ EXCEPT%B is used to add clone-limit exceptions.

There are 3 different kinds of exceptions
SERVER     - All users on this server[mask]
HOSTNAME   - All users with this hostmask
IP         - All users in this IP Netblock

The overall syntax isn't hard, just not well documented. Until
now.

OS EXCEPT SERVER ADD <name> <limit>
OS EXCEPT SERVER DEL <name>
OS EXCEPT HOSTNAME ADD <name> <limit>
OS EXCEPT HOSTNAME DEL <name>

and the only really different one, IP
OS EXCEPT IP ADD <IP[/mask]> <limit>
OS EXCEPT IP DEL <IP[/mask]>

Mask is in bits, like CIDR notation.
127.0.0.1/32 means 127.0.0.1-127.0.0.1
or say AOL
172.192.0.0/12 -> 172.192.0.0 - 172.207.255.255
172.208.0.0/14 -> 172.208.0.0 - 172.211.255.255

Sorry, it doesn't do the alternate CIDR format
172.192.0.0/255.240.0.0