To Set Up Dimension Style Overrides

Click Home tabAnnotation panelDimension Style. Find
In the Dimension Style Manager, under Styles, select the dimension style for which you want to create an override. Click Override.
In the Override Current Style dialog box, make changes to the dimension style by clicking the appropriate tab.
Click OK to return to the Dimension Style Manager.
The dimension style overrides are listed below the style they modify in the dimension style name list.
Click Close.