Because sometimes there are jobs waiting on the other officers that need to be done, and maybe they could not guess what is going to happen is what the obstacles that make the job done according to a specific period of time.
Because sometimes there waiting on me to be completed. And sometimes unpredictable obstacles that would have happened on the job not completed by the specified period.
Because sometimes there ahead of me to finish and perhaps could not predict that there will be obstacles, what happened to the job was done according to the time limit.