The dimension I'm using a product code, so the data set from which Only() is choosing is significantly cut down relative to the entire data set. It seems pretty straight forward to me - if Only() finds multiple RawDescriptions for the same product code, it should return Null() (I think?). In that case - output the string 'Multiple'. Otherwise, simply output the sole RawDescription that it found.
When I apply this expression, the product codes with multiple descriptions still return '-'.
