Steel member design - Staad Pro SS6 edition

In STAAD Pro SS6 edition (Version when a member subjected to Combined Axial force and bending, the member fails with higher ratios (i.e., 200, 216584 etc. ) according to section as per IS 800 - 2007 (LSD). But when I calculate manually for the Axial force and Moment for the STAAD section forces using the equation,

As per IS 800 - 2007, Section


I get Lesser value of ratios. Kindly confirm me, STAAD Pro SS6 edition (Version uses which formula, for calculating section  strength ratio for steel member design for code IS 800 - 2007