TChartPlotAreaPosition.RectangleStartsAtZero Property
In Excel 2003 or older, there is a margin around the plot area where no data can go. So, a Rectangle left of 0, meant to the start of the plot area + the margin. After Excel 2007 there is no margin anymore, and so you can place the plotarea at the actual 0 coordinates. If this property is false, it means the file was last saved by Excel 2003 and Rectangle includes margins.
Syntax
Namespace: FlexCel.Core
public Boolean RectangleStartsAtZero { get; }