Hi Lakhwinder,
We have analyzed your reported query. This is the default behavior and not an issue.
SplineAreaSeries will be rendering with given data points and few control points, which are used to draw the spline curve. These control points are calculated based on the given datapoints. Since, the axis scale range is calculated with control points too, the range has been extended to negative.
Control points are not required for the AreaSeries. So, the axis scale range is calculated from the give data points alone. Please refer to the screenshot for your reference.
Screenshot:
ScreenshotRegards,
Manivannan E