2.1.1486 Part 1 Section 22.214.171.124, order (Order)
a. 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.
b. The standard does not have any uniqueness restrictions on the order element.
Office requires the value of this element to be unique amongst any other order elements of the same collection containing the parent series element.