How many days are represented with the estimated sales?
The sales and revenue estimates in the JSLite and JSPro extensions, as well as the Product Database, represent figures for a 30-day period. However, that 30 days is 30 days into the future.
Basically, what that means is that if the product continues to sell at that particular Best Seller Rank (BSR), then the estimates you see in the extension and/or database would be the item's estimated sales and revenue for the next 30 days.
If you haven't already, you may want to read Greg's blog on the science behind our estimates. It is full of great information on our estimates and how they are generated. :)