Apocalypse Revealed # 559
559. "Knowing that it has but a short time." This symbolically means, because it knew that a new heaven had been formed, that a new church on earth was therefore imminent, and that it would then be cast into hell, along with its followers.
This is the symbolic meaning because the dragon knew that a new heaven had been formed, inasmuch as it had been cast down from it (verses 8, 9). It knew, too, from the prophecy in Revelation 21, that it would then be cast into hell, along with its followers.