This is a bug. I will get back to you soon with a fix.
I have sent you an updated version of the control via e-mail. Please, check it out and let me know if it fixes the problem.
another problem, the 100% piechart CANNOT be exported to PDF file, it threw exception:"Incorrect geomentry drawing type: System.Windows.Media.GeometryGroup"
I have e-mailed you new version of the control that should fix the PDF exception. Regarding the export of charts to Excel, it is something we intend to add, but I cannot give you any estimates.
I have sent you an updated version of the control that should fix this problem.