Revaluation is different from Rechecking. Revaluation is the process where the CBSE officials only check whether they have given marks on every question and whether the total is coming right.

Marks can increase or decrease depending upon the checker, and also upon the answer sheet. If there was any error in checking before then marks can increase or decrease depending on it.

Best of luck

Hi!
  If you are really confident then you can definitely apply for re-evaluation.
There are plenty of chances for getting extra marks after rechecking.
But for that you must be 100% sure with the answers you have written. And don't worry your marks will not get reduced if there isn't a chance of increasing.
Hope this helps!