Formula/formatting time

[Ron Purpura]

Hello All
I am hoping for some help in correcting a formula or insight into formatting..Not sure which one though.
In the attached spreadsheet, In cell B50, I am looking for the delta between c2 and b49. It seems I have an issue with my formula in B50. Whenever I have any time greater than or = to 24:00 hours in cell c2, my result reflects -00:00 in cell b50. I would expect the result to be 24:00. Not sure if it is a formatting issue ( which I cant seem to resolve) or a problem in my formula
Any help would be greatly appreciated
Thanks