The ANSYS Fluent manual [1] states in chapter 35.2.5.4. Defining Observable Objectives: When the chosen Objective is Target Change in Value, the field Target/Reference Change corresponds to the desired change in the value. When the chosen Objective is Maximize or Minimize, the magnitude of this field is a reference weighting for the observable. This can be used to normalize the objectives in cases where you have multiple observables of vastly differing magnitudes, thereby allowing the values entered for Weight in the Design Change tab to all be of similar scale. The attached document explains the process how Fluent applies the different objectives and the general principle of weighting.

Attachments:
1. 2049453.pdf