Classifieds at the time of posting this suggestion.

Unsolds are based on how long the listing has been up; Listing has been up 5 days and item been in the sellers inventory for 8 days? It has been unsold for 5 days.

The age of the listing(s) are shown in the screenshots rather than the last bump - Unsolds and item histories are presented in chronological order according to the screenshot(s).

x1 for sale at 2.5 Keys - http://i.imgur.com/iOLXXyY.png

Unsold for 19 days http://backpack.tf/item/318188486

-

User also has an Outpost trade; http://www.tf2outpost.com/trade/28395682 - 2.5 Keys - Unsold for 2 weeks - Autobumper.

Only 1 seller, no buyers.