Net change basically means that when you're done with EVERYTHING, how far did you move from the beginning.
So in this case, let's say that you started up on the 1st floor, you went up to the 5th, down to the 2nd level of the garage, up to the 1st again then up to the 2nd floor. You started on the 1st floor and ended up on the 2nd floor, so the NET CHANGE is 1 floor up. sound clear?