GOT IT!
=Floor(Fields!Time.Value*3600 / 3600) & ":"& RIGHT("0" &Floor(Fields!Time.Value *3600/ 60) - Floor(Fields!Time.Value*3600 / 3600) * 60, 2) & ":"& RIGHT("0" & Fields!Time.Value*3600 - Floor(Fields!Time.Value*3600 / 60) * 60, 2)
and this is for the sum
=Floor(Sum(Fields!Time.Value*3600) / 3600) & ":"& RIGHT("0" & Floor(Sum(Fields!Time.Value *3600)/ 60) - Floor(Sum(Fields!Time.Value*3600) / 3600) * 60, 2) & ":"& RIGHT("0" & Sum(Fields!Time.Value*3600) - Floor(Sum(Fields!Time.Value*3600) / 60) * 60, 2)