That question – "To what extent do the prophets understand their own prophecies?" gets right to the heart of this mystery of the inspiration of prophecy, how the words that the prophets speak in their own consciousness are God's words and not their own, so that, what's first and foremost important is God's intentions in those words, whether the prophets understood them or not. But I think we should believe that, as they're prophesying, they also understand a lot of the import of what they're saying. 1 Peter 1:10 and following give us, address this question fairly explicitly, that the prophets had an inkling, at least, of what they were prophesying about, but were still searching for who and what and where these prophecies would be fulfilled. I think part of the nature of prophecy is, or a large part of prophecy is, that the prophecies themselves are generated out of prior promises that God had revealed, particularly the promise, the threefold promise to Abraham, of seed, land and a blessing to the nations, and the promise to the house of David that God would adopt David's son as his son; he would be a father to him; he would not take his covenant loyalty away from his son, and that his son would build a temple in Jerusalem. Out of those two cardinal promises, we could say, in the Old Testament, all of the rich and varied pictures of the salvation restoration that the prophets proclaim are just so many instantiations, realizations of those promises. We might call the prophets "painters of the impressionistic school." They're using as the paints in their palette previous deliverances from Israel like the exodus, the promises to Abraham, the promises to David, and they're projecting those forward in an impressionistic way, and they are talk * they are referring to a real future which will come about, but a future that's not to be understood necessarily in a literalistic way as corresponding in any sort of one-to-one way to the images that they use in depicting that future.