Time Calculation in the SSRS

Hi Experts,

I want to do small Calculation but I was getting wrong values. Could anyone check the expression please. 

I was calculating 'Not accounted for/Overtime' by using below expression but I was getting wrong values. Could anyone guide me where I was doing mistake please 

("0"& INT((7-SUM(Fields!TaskStatusMinutesDuration_New.Value)/3600))&":"&IIF((INT((SUM(Fields!TaskStatusMinutesDuration_New.Value) MOD 3600)/60))=0,"00",
(IIF((INT((SUM(Fields!TaskStatusMinutesDuration_New.Value) MOD 3600)/60))<10,"0"&INT((40-(SUM(Fields!TaskStatusMinutesDuration_New.Value) MOD 3600)/60)),
INT((SUM(Fields!TaskStatusMinutesDuration_New.Value) MOD 3600)/60))))&":"&"00")