As a consultant, if an applicant's writing is concise and the essay is strong, I will usually "okay" a 10% overage. There is no point in making yourself crazy over 5 or 10 (or 30) words.
However, I believe that in sum, the essays should not run 10% over, so, if one is a little long, try to make another one a little bit short. I think of it as the Stanford rule. Stanford asks that you use 1800 words total and spread them out as you see fit. (For Stanford I recommend that you stick with the 1800 as your maximum!).
Remember, if another applicant can convey his or her point in 500 words, it won't reflect well on you if you need 600 to do so!
