This function returns the namespace URI prefixed to the primary numbered list block tag specified in the document type configuration file (.dcf) for the document type associated with doc. This tag is inserted when users select the numbered list button on the Application toolbar.

If a tag name is returned, numbered_list_block_tag_name function returns arr.

The function returns the null string if there isn't a namespace prefix, if no numbered list block tag is designated for the document type, or if doc is invalid or an ASCII file. If doc is omitted or 0, the current document is used.