If we put this into an equation it will make this easier. Lost four would stand for negative four or -4. Gained nine would plus or positive nine or 9. Put this together we get the following equation: 9-4 From there you can get the answer easily since that is like 1st grade math. The answer is that the total change is 5 yards.
One way is It could show the increase and decrease of an item and the seconded way is it could show how much it has increased or decreased over a period of time