2.1.1414 Part 1 Section 18.104.22.168, axId (Axis ID)
a. The standard states that 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.
b. The standard does not place any restrictions on the val attribute of the axId element.
Office requires that the val attribute of this element matches the val attribute of an axId element on a catAx, dateAx, serAx, or valAx element on the chart.