PIX 501 License Issue

I have a PIX 501 out at a client site that has a 10 user license. However we have 12 computers on that site. Is the license in reference to setting up a VPN or is it total number of devices that can be connected to the PIX? We only need 5 of the computers on the VPN and the rest just need internet access so is there a way to configure a range of IP address' to connect to the VPN and than allow the rest just internet access on the assumption that the license is for VPN access. Any ideas and help would be great.