2.1.839 Part 4 Section, rcmt (Revision Cell Comment)

a.   The standard specifies that @author is restricted to be of type ST_Xstring.

Office defines that the length of @author should be between 1 and 52 inclusive.

b.   The standard places no restrictions on the relationship between the guid attribute and a revision record.

Office uses the guid attribute to associate a revision record with a comment in a worksheet.