Load Builder-Proportional Distribution by Area Method- Total Calculated Demand Exceeds the Total Flow in the GIS Layer

I am using the Load Builder and the Proportional Distribution by Area Method to compute the load from GIS Data. I have the Theissen Polygons created from a districts layer that have the flow data as well. Iam using the same layer to compute the flow. The problem is that the total flow calculated based on the Load Builder exceeds the total flow in the GIS layer itself calculated manually.

I have checked the coverage of the Theisen polygon; it is overlapping exactly with the flow layer. Any justification for this ?