Cloud Failover Appliance (CFA) defines a client as the configuration set of files and directories on a networked computer. This is not to be confused with the agent installed on the networked machine itself. Each physical machine can have many sets of files and directories, and therefore can be referred to by many client entries. While there are no hard limits to the number of clients that you can add to the system, there are practical limits to the number of clients.
As a general rule, the capacity of your CFA should be approximately double the total amount of client hard disk space. Following this rule will ensure that you have reasonable space for newly modified data after each client has been completely backed up.