There is not much difference in computation time for setting Pretension Force vs using Adjustment.  The default is Preload Force because that is what is created when a Bolt Torque is specified on a drawing. The Adjustment is generally unknown because no one bothers to compute Kpart and Kbolt to compute Keq to use the Preload Force that is calculated from the Bolt Torque in order to input an Adjustment.  Just input the Preload Force.