This comes from the text of the Magnitsky Act:
(c) Form of Report.–
(1) In general.—
Each report required by subsection (a) shall be submitted in unclassified form, but may include a
classified annex.
(2) Exception.—
The name of a foreign person to be included in the list required by subsection (a)(1) may be submitted in the classified annex authorized by paragraph (1) only if the President–
(A) determines that it is vital for the national security interests of the United States to do so;
(B) uses the annex in a manner consistent with congressional intent and the purposes of this
Act; and
(C) not later than 15 days before submitting the name in a classified annex, provides to the
appropriate congressional committees notice of, and a justification for, including the name
in the classified annex despite any publicly available credible information indicating that the
person engaged in an activity described in section 3(a).
(d) Public Availability.–
(1) In general.—
The unclassified portion of the report required by subsection (a) shall be made available to the
public, including through publication in the Federal Register.
(2) Nonapplicability of confidentiality requirement with respect to visa records.–
The President shall publish the list required by subsection (a)(1) without regard to the requirements of section 222(f) of the Immigration and Nationality Act (8 U.S.C. 1202(f)) with respect to confidentiality of records pertaining to the issuance or refusal of visas or permits to enter the United States.
So you can see that what Congress gets is different than what the public gets.