Those are the ones we know about. If you think about the problem, it really is a very difficult one to solve. We're attempting to find and track tiny objects that could be anywhere in an absolutely massive volume of space using almost entirely ground based equipment that is hobbled by competing demands, atmospheric distortion and a very inconveniently nearby star that halves the observation time and makes it really hard to find objects on that side of our orbit. For all the fancy animated maps of the many asteroids we have located there are likely still a very large number of other asteroids we don't know about yet and may not find out about until after the fact.