Bissey, I dont think there will be a problem if the tutoring company can testify on your behalf that they originally intended to hire you for 20 hours but were not able to get you the number of hours. Tara just in case try and register as volunteer at the University of Arizona, that will help clear any doubts that the USCIS may have. And I dont think that the USCIS will have a problem until you can produce a valid paystub. Don't worry bro.

Your old friend.