The manual isn't very clear, the Radar License Requirements section says:
Radar functionality is controlled by capacity licenses installed on the controller and activated as an option key (for more information on the Option Key, see Applying Product License Keys). Radar capacity licenses are only required for In-Service and Guardian scan profiles. Any AP assigned to an In-Service scan profile counts as 1 against the licensed Radar capacity
The maximum number of APs that can be licensed for Radar is twice the platform limit for local APs. Once the maximum number of APs is reached, no new licenses can be installed.