Hi,
Because of i have missed the floor function formula giving you incorrect result.
Use below formula..This will give you the correct result. I have missed the Floor function for positive numbers. If you compare the old formula and new one floor is missing as highlighted.
=If([Column_Name]<>[Column]) Then "-"+FormatNumber(Floor([Column]/3600) ;"0") + ":" + FormatNumber(Floor(Mod([Column];3600)/60);"00") + ":" + FormatNumber(Mod(Mod([Column] ;3600) ;60) ;"00") Else FormatNumber(Floor([Column]/3600) ;"0") + ":" + FormatNumber(Floor(Mod([Column];3600)/60);"00") + ":" + FormatNumber(Mod(Mod([Column] ;3600) ;60) ;"00")
Regards,
Amit