Path to the preferences:
Menu Window > Preferences
Dialog Preferences > Formulas > Debugging
In the default setting, the branches of a formula are also calculated and represented in the Formula Inspector that are not relevant to the determination of the result. Results of non-relevant branches are represented in gray. To suppress the evaluation in the formula inspector, the check box Enable inspection of non-evaluated conditional branches in the formula inspector must be deselected. Branches whose evaluation are not relevant to the result will then be marked as Not evaluated!.