You are provisioning a Window 2008R2 server for remote desktop service; you've configured the terminal services license manager in one mode [ device | user ]. But when you receive the license documentation you discover that the CALs purchased were for the other mode. Then the Windows terminal license server manager tells you to change the mode of the license server.... but there is no obvious way to change the mode [because Windows is user-friendly!]. One option is to go old-school - hack the registry!.
First, stop the license server. Then in regedit change the value of the "LicensingMode" key in the "HKEY_LOCAL_MACHINE \ System \CurrentControlSet \ Control \ Terminal Server \ RCM \ LicensingCore" collection. A value of "2" indicates per device licensing and a value of "4" indicates a value of per user licensing. Then reboot.