problem with facePostProcessing
 

Hello foamers. I am simulating a sprayFoam case and I have applied stick condition to a wall so that particles, when they reach the wall, stick there.
I have also applied facePostProcessing on that wall to see how much mass is accumulated and the mass accumulation locations.
But the facePostProcessing output shows an anomaly. It outputs that the mass accumulated is greater than the total mass that is injected (below I have attached figure). Why is this happening and how to rectify it?