God has given us the Word to read, and He has given us the Holy Spirit to help us understand, but while we are on this earth in fleshly tabernacles, we are not privy to all of His ways. For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known. Our understanding right now is in part, we are not yet given the understanding of all things (we will have it later in glory, according to the Apostle Paul).
Until God has fulfilled the prophecies that are yet unfulfilled, our understanding of those fulfillments is imperfect. Our understanding amounts to educated guesses. We know God, and based on that knowledge of Him, we can make an educated guess as to how He will do what He has promised to do.