strange place

hey all,
i was just wanting to know what the “last changed” heading in the infected files chest means ? I went to download Linux from the distributor’s site by typing in the url and as soon as i hit download, avast announced a trojan caught???
the infected date was correct but last changed was dating back to last year??? Is this when I recieved the virus or did I get the virus from the Linux distro???

This field is just the original timestamp of the file (before it was transferred into the Chest).