Smooth area series always support the Value and Label data point values. If the Combo Chart Subtype is set to XY Scatter, the smooth area series will accept a X data point value.
Smooth Line series are created for values data groupings displayed in combo charts, the Series Type of which is set to Smooth Line. Smooth Line series currently do not have any series specific options.
Smooth area series always support the Value and Label data point values. If the Combo Chart Subtype is set to XY Scatter, the smooth area series will accept a X data point value.