The Fit To Datums check box in the Position dialog box (Insert | Dimension | Position) determines whether or not PC-DMIS calls the fitting algorithm when datums are used.
When selected, PC-DMIS calls the fitting algorithm when datums are specified. It reports the considered feature in the fitted position with the total bonus being the remaining available bonus after fitting.
When cleared, PC-DMIS analyses the Position dimension with features in their measured position with no fitting applied. The reported total bonus is the total available bonus from the considered feature and the datum according to the datum constraints.