2.1.803 Part 4 Section 18.104.22.168, mpMap (Member Properties Map)
a. The standard states that @v is an index into the shared items table...
Office treats @v as an index into the cacheFields collection.
b. The standard states that the values of the v attribute are defined by the XML int datatype.
Excel restricts the value of this attribute to be at least 0 and at most equal to the value of the cacheFields count; the value of the memberPropertyField attribute on the cacheField pointed to by this value must be true.