Is that the 'exclusive bonus estimator' you are talking about?
It looks like you can change the monthly growth from 5-15% so you can be as optimistic as you want. It is still a little unrealistic however. 10% growth in uploads is a LOT less work when you have 10 images, than it is when you have 10,000 images.
I'm guessing if it took 3 months to get 500 sales, in another 3 months you will have 500 sales from the new images plus perhaps 750 from the old image making 1250 downloads.