Thickness is only supported for 3-D Pie Chart. It does not apply to 2-D Charts because flat pies have no thickness.
The valid range of values for the thickness of the pie are from 0 to 40.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2