By default, the AllowStack property is True. The AllowStack property specifies whether the series are stacked based on the non-empty values defined in the Stack property. When enabled, the series values are visually stacked on top of each other; when disabled, they are displayed independently. The Stack property specifies whether the serie is stacked (same value for multiple series of the same type indicates same stacking-group). The Type property specifies the type of the serie (the way the data is represented).

The following screen shot shows two series stacked (AllowStack property on True, and both Stack property points to the same non-empty string):

The following screen shot shows two series stacked (AllowStack property on False, and both Stack property points to the same non-empty string):