What's up with my Steam?

So something's wrong with my Steam account. Or at least, the way it counts my gameplay time.
I was looking at my account when I suddenly saw that I was "in-game" Stalker: Call of Pripyat, and I definitely wasn't. So I went to my library and saw that my account says I have played the game for 246 hours... When I definitely only started it once a long time ago when I bought it off a sale. So what's up with that?

I've seen a similar problem with Raptr, saying I've played games much longer then I actually have

Huh, that is weird...I had a similar problem a while ago where it said I had played Batman:AA for 0.1 hours even though I had finished it.

i dont pay attention to that a whole lot.. as apparently ive played DoWII more than i have CSS which i KNOW isnt true