Calibrating scales gives the user the ability of creating a scale for a drawing when a scale may not be shown for a drawing or a detail, but one or more dimensions are specified on the drawing. In this case, you can specify the scale by "Calibrating" it.
Drawing Scale Edit Window
Detailed Scale Edit Window
Click on the link below to view a video on Calibrating Scales.
Click on the link below for Online Help Documentation.
Calibrating Scales Documentation