Merge remote-tracking branch 'origin/feature/10581_improve_reflredoneauto_docs'

Code/Mantid/docs/source/algorithms/ReflectometryReductionOneAuto-v1.rst

@@ -11,7 +11,13 @@ Description
 
 Facade over :ref:`algm-ReflectometryReductionOne`.
 
-Pulls numeric parameters out of the instrument parameters where possible. You can override any of these automatically applied defaultsby providing your own value for the input.
+Pulls numeric parameters out of the instrument parameters where possible. You can override any of these automatically applied defaults by providing your own value for the input.
+
+If ProcessingInstructions is not set its value is inferred from other properties:
+
+* If AnalysisMode = PointDetectorAnalaysis and PointDetectorStart = PointDetectorStop then the spectrum specified by PointDetectorStart is used.
+* If AnalysisMode = PointDetectorAnalaysis and PointDetectorStart ≠ PointDetectorStop then the sum of the spectra from PointDetectorStart to PointDetectorStop is used.
+* If AnalysisMode = MultiDetectorAnalaysis then all of the spectra from MultiDetectorStart onwards are used.
 
 See :ref:`algm-ReflectometryReductionOne` for more information on the wrapped algorithm.