2.1.1543 Part 4 Section 188.8.131.52, pie3DChart (3D Pie Charts)
a. The standard states that multiple ser elements may be specified on this element.
Office only displays the first series if there are multiple ser child elements.
b. The standard states that the maxOccurs value for the ser child element is unbounded.
Office limits the occurrences of this element to 255.