2.1.446 Part 4 Section, encoding (Output Encoding When Saving as Web Page)

a.   The standard requires that this setting is roundtripped as specified.

Word does not roundtrip this element when the specified encoding is equal to the current default encoding, or when the specified encoding is not supported.

b.   The standard does not limit the length of the value of the val attribute.

Word restricts the value of this attribute to be at most 255 characters.