Absolutely nothing. The very fact that you wrote this shows that you take notice when you look at the clock at 11. This means you will remember it better than all the other non 11 o'clock times you look at your clock. Also, it could be something like that's when you go to bed, or when your favourite TV show ends or something like that.
Depends an where it is. If it's before the colon (11:) it's the Eleventh hour (See Doctor Who) After the colon (:11) it's eleven minutes after the hour.