1) Each portion or paragraph has its own classification.
2) Even a single word may classify or raise the classification level of a portion.
3) The "header" or document" classification can be no lower than the highest portion classification. However, it is possible that the overall classification can be deemed to be higher than that of any single portion.
4) Therefore, it's possible that the redaction of a single word can down-class -- or, even allow declassification of -- a lengthy, highly-classified document.
5) For, example, during the Manhattan Project, "uranium was just such a word.
6) "Congress critters", per se, cannot perform classification / declassification. There are specific individuals who are trained and authorized to classify and declassify sensitive materials.
I cover this in my video, using declassified FBI documents as examples -- and HRC as an example of a "Classifying Authority" -- who never did her job...
Trump of course can declassify it.
And what I said still holds—far too much is deemed “classified” and classified at too high a level.