actually, the game uses a math runner system, like any game. Due to the limitations of that math system, the largest number the game can handle is about 2,147,483,647, meaning that 2,147,483,647 is the bottom. If you go down from that floor the game will crash and you will cry for weeks.
The bottom of the dungeon is actually that number level because the fate game goes to double of that. The rest of the numbers are treated as negative numbers. Also that is the top "number" in Fate, for levels, health, gold, skill points, and everything that goes by the numerical system on Fate. You exceed any off them and your screwing the game up, but if you exceed the numerical level in dungeon levels, the game is faced with writing its own code for level negative one. You would be screwing up the game itself then, not just YOUR game.