XR18 Precision Limiter - How to use?

Hey guys, I am trying to set a limiter on the Main Out of my XR18 to boost my stream broadcast mix and protect it from clipping. The only limiter FX on the XR18 is the 'Precision Limiter' which doesn't have a threshold to set. Does anyone know how this Precision Limiter works? Also, the GR meter doesn't engage on the Xair iPad app.


 


Are there any ways around this FX Plug in or anything I can do to have a make-shift Limiter on the XR18?


 


Feedback to Behringer on the XR18 - could you add another standard Limiter plugin on the XR18?