2.1.1696 Part 4 Section 18.104.22.168, formulas (Set of Formulas)
a. The standard states that the maxOccurs value for the f child element is unbounded.
Office limits the occurrences of this element to 128.
b. The standard does not restrict the number of instances of the formulas element.
Office allows at most one instance of this element in each place where it can be used.