This thread is for those who are already in US. Let me briefly answer: you cannot correct the entry form. The only thing you can do is to write the correct city to the forms from now on, and have a very good explanation why he did that mistake, and hope that he doesn't get disqualified. If both cities are in the same country; or one is like a suburb of the other, you may have a chance; but usually this kind of mistake is grounds for disqualification. You may want to contact the embassy/consulate and ask for information.
Thank you for your replie. Yes, we are already in the US and going to do AOS. Yes, the same country and it says on his birth document that it was submitted to that city that he wrote. I hope it is going to be OK. Should we contact attorney about it? I am really worried now.