If the Postal Service determines that any document or portion of a document, or other matter, which it provides to the Postal Regulatory Commission in a nonpublic annex under this section contains information described in section 410(c), or exempt from public disclosure under
section 552(b) of title 5, the Postal Service shall, at the time of providing such matter to the Commission, notify the Commission of its determination, in writing, and describe with particularity the documents (or portions of documents) or other matter for which confidentiality is sought and the reasons therefor.