Hi,
In order to find the number of client connections, you can run the command "status detail" from the CLI.
This information can also be found on the GUI > Monitor > System Status > Proxy Traffic Characteristics >Connections.
Further details of client activity is in GUI > Monitor > Client Web Activity
If you want further reporting and create custom reports, you can go for the Cisco Ironport Security Management Appliance. For further information about the SMA, you can go to
http://www.cisco.com/en/US/partner/products/ps10155/tsd_products_support_series_home.html
and
http://www.cisco.com/en/US/partner/products/ps10155/prod_release_notes_list.html
For further assistance on pre-production issues, you can open a case at http://www.cisco.com/web/partners/tools/pdihd.html
Regards,
Kush Srivastava
Cisco PDI Help Desk
http://www.cisco.com/go/pdihelpdesk