Request clarification of @datatype on new lcSequence2 element

In the lang spec topic for the new (to DITA 1.3) element lcSequence2, the attribute table says that there is a required @datatype attribute.
The description says "The datatype for this data", and there is a listed default value of "Use numbers for sequence".
I'm not sure what that means - but the samples in the topic also show <lcSequence2> with no @datatype attribute (they only use @name and @value).
Questions in order of priority:
1. Is this attribute really defined for lcSequence2?
2. If so, is it really required?
3. And if it is really defined, what sort of value should be entered?
Thanks - Robert D Anderson IBM Authoring Tools Development Chief Architect, DITA Open Toolkit ( http://dita-ot.sourceforge.net/ )