All you can do is increase traffic. Any ranking above about 8-10k can safely be ignored. Once into that territory, it is pretty hard to influence all (believe, I've studied this indepth, and I can't see a way to influence it other than by traffic.)
Now, up there in the stratosphere of 20k+ and on up rankings, nobody really believes those to be all that accurate. Those sites just aren't getting enough traffic to accurately measure. Like ncw said - install the toolbar and you your self can pull it down to say - oh - 40 to 50k in a few weeks time.