Resource Original Duration is not Equal Activity original duration

 Hai

In my Subcontractor submitted Programme some of the Resource Original Duration is not Equal Activity original duration .

This issue occur where single activity have Multiple resource . 

Activity Type is task Dependent , Duration type is Fixed Duration & Units /Time, Percentage Complete is duration

Can you say may  what is the cause that affect in multiple Resource Assignment Original Duration not equal activity original  Duration 

Is there any filter to find Where Activity Original Duration is not equal to Resource Assignment Original Duration 

Currently I am Organize by Activity in Resource Assignment window with Column Duration &  Editing it manually

Thanks