When you type a number in Excel 2013, you will see all of the dependent cells in the visible window animate with the new result dropping in to the cell as if it were a slot machine.
This is one of those beginner features introduced in Excel 2013 to show new Excellers that when you type a value in one cell, Excel is going to the trouble of updating all of these other cells. It seems silly, doesn't it?
However, there is an expert use for this feature. Subconsciously, your mind will start to notice the cells that are not animating that should be. Perhaps one of those new Excellers added with a calculator instead of the AutoSum and hard-coded an answer. You can actually spot these when you notice the total is not animating.