As per my experiment, product ranking is based on "Download Last Week". No sub sorting available.
Most software products on the C/Net Download page have a product ranking. This information usually resides in the lower left information panel for the product which also lists the version, etc. We have a few questions related to this ranking:
1. What is the product ranking? An editor, consumer, or other type of ranking?
2. The product rankings are never in order regardless of whether we choose to sort by customer rating or editor rating. This is the case even if all filters are OFF to lesson the chance it will eliminate ranked products.
3. If we sort by editor rating, can we then sub-sort by date of rating? A list of editor choices cluttered with a bunch of old products is not very useful.
Thank you for any help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic