Yes, you must have misunderstood it.
The rect would be defined through the the two points (left, top) and (right, bottom).
Both can be calculated from each other and thus it's just a question of preference:
1) (right, bottom) = (left, top) + (width, height)
2) (width, height) = (right, bottom) - (left, top)
This is not the first time this has been brought up, so make sure to use the search engine.