Hello,
When you set the service policy on the firewall, it is always for the whole class of traffic. So, your bandwidth calculations will also be for the whole class. While the documentation seems to be not very clear, here is some information about rate limiting.
http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a008084de0c.shtml#rate
If you look at the example configuration, they talk about the whole class bandwidth instead of individual user bandwidth.
Hope this helps.
Regards,
NT