I got my original 3GS on release day in June 2009 as an upgrade to a 1G. In around September 2009 it developed a problem with the mute switch so I had it replaced at my local Apple Store.
A friend just asked me what my data usage is (as he is looking at his first smart phone contract and doesn't know how much data allowance to include) so I checked my stats on the 3GS.
It says at the bottom Last Reset: Never so my question is, when does Never begin?
My current 3GS was restored from the backup of my original 3GS when it was replaced and I'm not 100% sure but I think that the original 3GS may have been restored from the 1G.
Does my usage stat include only the current 3GS or does it include the original 3GS usage (and possibly the 1G usage if I restored from it) as well?
EDIT: Following Cawas's answer, here are my current stats for illustration: