Question about EXI Draft - Position of Self-Contained

Dear W3C EXI WG members,

I have a question about this draft specification.

EXI has Self-Contained option (ref. S.5.4).
And the EXI parser can parse Self-Contained data without parsing other
parts of the EXI document.
But how does the EXI Parser find the position (ex. bytes offset) in the
EXI data?
If the EXI parser wants to parse Self-Contained data first, can it get
a start position of Self-Contained data from the EXI documents?

Regards,
Keisuke Tamiya (tamiya.keisuke@canon.co.jp)