Allows you to change the size of the object you are loading in, simple as that ! your scaling the object.

Another advantage is that often when 3D objects are made they dont appear the correct size in game, they need to be scaled. This option allows you to do just that while comparing it to the properly scaled Jazz model.
You can just leave it at that, or if you like go to an editor and rescale the object using the detiails from the level editor.

So yeah im resizing a fair few objects at the mo.
Oh as far as scaling goes 100=100% of the size...so to double the size you type 200 and to half it you type 50 etc.