It goes back to the tree that was cut down and banded to prevent it from growing. The, after 7 "times" the bands were removed and the tree was allowed to grow again.
According to Adventists (and later CT Russell), this not only applied to Nebuchadnezzar, but to Jewish rule as well. In theory, the Jewish nation was God's nation on earth. It ended when it was conquered by Nebuchadnezzar in what they like to say was 607 BC. It is banded for 7 times (which they figure as 2520 years), ending in 1914, when a God-ruled nation will return.
This is so full of holes. We know 607 was wrong. Secondly, exactly what was taken away or withdrawn at that point? Was God still ruling Israel up until 607 (well, 586/587)? The kings were all wicked. They were merely puppets for whoever was ruling them, whether it be Egypt or Babylon. And what of the Jews returning after being freed? Wasn't that a restoration? What about when Israel became a nation in the 1960's? Couldn't you say Jewish rule was restored then? And what of 1914? Did God really step in back in 1914? Not exactly - the "Gentiles" are still ruling. Several nations have been founded and other have fallen since 1914. One can hardly say their time has ended. What's more, the prophecy was for a non-Jewish king. A king who worshiped other gods. Why would a prophecy about this king also apply to God's kingdom? In other words, God's kingdom is supposed to be the "greater Nebuchadnezzar". Even if you buy all the "greater Moses", "greater Noah" crap, you've gotta have a problem comparing such a righteous thing (in their eyes the culmination of everything in the Bible) to a king who never worshipped the Jewish God.