SAP Message RSBCT_PBPC024 - Variable &1 in BRF expression &2 does not have any single value assigned

Diagnosis
The BW Variable &V1& used in BRF Expression <(>&<)>V2<(>&<)> does not co
ntain a valid single value. Only BW Variables that return a singlevalue can be used in the BRF BI Planning Connector (BBPC) BW Variableexpression type for BRF.