Clarify DAQ policy for injected parameters

source/daq_policy.rst

@@ -37,3 +37,5 @@ These can be set up programmatically:
 The policy can be overwritten from the GUI, before instantiation, and saved in a project:
 
 .. image:: graphics/daq_policy.png
+
+Injected properties, however, can only define their policy at the time of injection.