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 seller at 0.33 Refined - http://i.imgur.com/Tw5kNIH.png

Unsold for 5 days http://backpack.tf/item/551929285

Outpost sellers.

Only 1 seller selling it in a set.