Usually there is no descriptive test for FIA. However, the commission may conduct descriptive test if it finds some scams in the screening test as it was noticed previously in the screening tests of FIA and FBR. The criteria of shortlisting for interview is 5 candidates per post if the number of seats is less than or equal to two and 3 candidates per post otherwise. So in order to be safe you must score 85+ to be called for interview.