Compute Distinct Count (computeDistinctCount)
The Compute Distinct Count property specifies whether or not the number of sub elements should be computed for a dimension.
Sub elements are either sub dimensions or, in the case of the innermost dimension, fact rows.
Considerations regarding chart
                drawing and output sorting: When selecting a chart visualization (specified by Draw
                        As) that displays aggregated values, aggregation must be
                performed on the dimensions required by the chart. Similarly, output sorting
                requires an aggregation function to be defined for all dimensions by which these are
                sorted. If more then one aggregation option is selected, the processor picks the
                aggregate option that is highest in the priority list:
        Type: Boolean.
Default value: FALSE.
You can find the Compute Distinct Count property in the Value category of the Properties view.