Project Start Time 22-04-2015 12:30:00
Project End Time 24-04-2015 20:30:00

Shift Start Time 11:00:00
Shift End Time 21:30:00

The total time spent on the project is 29 hours but a simple subtraction is not working and is giving me 56 hours as its taking time beyond Shift End Time 21:30:00.

Any suggestions on how to get this regularized.