Cisco VPN Client - Subnet Range

Hi.  I created a VPN on my XG firewall for Cisco VPN clients (IOS devices).  I can connect fine, and connect to some of the devices within my network.  I set up the XG so that the VPN clients use (say) 10.10.75.1 to 10.10.75.20 within my network, but they seem to be in subnet 10.0.0.0/8.  I want to restrict the range of the subnet which my VPN uses.  How can I achieve this?

Thanks.