MC.9 report is showing -ve value when MRP controller selected

Hi Expert,

I'm confuse about the -ve value in MC.9. If i run by using Plant as the selection parameter for month 02.2010, then sorted by valuatted stock value(ascending), it will not show me the -ve value for all materials. But if i run the report by using Plant and MRP controller as the selection parameters,then sorted by valuated stock value(ascending), it shows me the -ve value. why?

Please explain.

Thanks