now what?(N-400)

I had my N-400 interview about two weeks ago.
And I just got a letter from INS office where I had the interview and said "please come to the office shown below at the time and place .....".
It's form G-56 and it says ASK FOR: DAO / REASON FOR APPOINTMENT : to sign N-400.
what does DAO mean? I signed my N-400 after I passed my interview/test.
It's even somewhere next month.
Anybody ever got this kinda letter or got through?
thanks.

I had my N-400 interview about two weeks ago.
And I just got a letter from INS office where I had the interview and said "please come to the office shown below at the time and place .....".
It's form G-56 and it says ASK FOR: DAO / REASON FOR APPOINTMENT : to sign N-400.
what does DAO mean? I signed my N-400 after I passed my interview/test.
It's even somewhere next month.
Anybody ever got this kinda letter or got through?
thanks.

At the time of interview in Immigration Office, may be they forgot to get your signature on the certification as to truth of information stated in the Form. It is done after interview. You should contact them asap. if you will fail to appear then it can dealy in decision on your applicationl. This letter is from their Adjudication Office.
Good luck.