The Statement is sent using a Content-Type of multipart/mixed. Any Attachments are placed at the end of such transmissions.
For starters, the Statement is not sent; the request (or "transmission") is. So that should be improved.
It's possible that the second sentence--which lacks some technical specificity--could be removed entirely as a result of other nearby requirements. Namely:
The first part of the multipart document MUST contain the Statements themselves, with type application/json.
and
Each additional part contains the raw data for an Attachment and forms a logical part of the Statement. This capability will be available when issuing PUT or POST requests against the Statement Resource.
Currently, the second item under "Procedure for the Exchange of Attachments" says this:
For starters, the Statement is not sent; the request (or "transmission") is. So that should be improved.
It's possible that the second sentence--which lacks some technical specificity--could be removed entirely as a result of other nearby requirements. Namely:
and