Cross sections within 1/6 span from supports or 1/6 span from midspan are considered "at critical sections".
If the design section is not declared as post-tensioned in the design section or design strip segment, then the Pe/Ag and Pee terms of 8.1.6.1 are assumed to be zero (even if the cross section includes tendons), where Pe is the total effective prestress force considered.
Cracking is assumed to be top (negative moment) or bottom (positive moment) based on the "Min. Reinforcement Pattern" selected in the design strip segment or design section.
See ""Cracking Moment" Used in Design Calculations" for a theoretical discussion of the "cracking load".