Rectification of order u/s. 143(1)

Dear all,

I have received order u/s. 143(1) for the return e filled by me which was filed u/s. 44AF for F.Y.  2009-10.

In the return, it was as under:

Sales -  100

GP -        12

Exp -        3

NP -          9

But in order made u/s. 143(1), exp was taken as '0' and then NP became - 12. It was the mistake of a software while preparing xml file. Now I want to rectify the same but I found on the net that if total income is changed in the order then rectification of the same will be rejected. Now pls suggest what should I do?

Also tell me what is the time limit within which rectification must be filed?

Thanx in advance.