2.1.749 Part 4 Section 3.9.4, futureMetadata (Future Metadata)
a. The standard specifies that the values of the count attribute are defined by the XML Schema unsignedInt datatype.
Office requires that @count has a maximum value of 2147483647.
b. The standard states that the name attribute is the metadata type name.
Office requires this name must be equal to the name attribute of one of the metadataType records in the metadataTypes collection. This name must be unique among all futureMetadata records and must not equal XLMDX.
c. The standard states that the possible values for the name attribute are defined by ST_Xstring simple type.
Office requires that the name attribute be non-empty and less than or equal to 65535 characters.