When the IsLabelAutoFit property is set, the Chart control automatically fits the labels along the axis by determining font sizes, angles, and offsets that work best for your chart. This eliminates the need to manually adjust label options along the axis.

When IsLabelAutoFit is set to True, the LabelAutoFitStyle property specifies the styles that the Chart control can use to automatically fit the labels. If IsLabelAutoFit is set to False, the LabelStyle object's Font.Size, Angle and OffsetLabels properties determine label font size, label angles and whether or not labels are offset. 

When you set the  Font.Size, Angle or OffsetLabels properties in the LabelStyle object, IsLabelAutoFit is automatically set to False.