It's scored where the mean is 500 and the standard deviation (a measure of how spread out the values are) is 100.
Since on the real test the mean was 217 and the standard deviation 24, a 470 would work out to...209 or so. In other words, pay close attention to your worst areas on that thing and study them harder. It's good that you're thinking about the test this early...you should be able to get that up.
The thing's pretty damn good...predicted my score within a few points...