2.1.1526 Part 1 Section 220.127.116.11, secondPiePt (Second Pie Point)
a. The standard states that the contents of the val attribute are interpreted based on the context of the parent element.
In Office, the val attribute is a zero-based index into the chart's data series that must be unique amongst secondPiePt elements within the same collection.
b. The standard states that the values of the val attribute are defined by the XML Schema unsignedInt datatype.
Office restricts the value of this attribute to be at most 2147483647.