ChemicalX, It's good news that she has spotted out the error before the interview. Do like these people state above. Pay extra and get it as soon as possible. Make sure you get that corrected copy of your I-20 before the interview. Incase(I hope this dosent happen!) If you dont get the I-20 and you have an interview. Then Let the person who takes the interview know that there is an error and it is going to be corrected and this has been brought to the university attention. If they delay sending your I-20 then ask the school international student advisor to write an email explaning the case to the U.S Embassy. Print that paper and present during the interview. I hope she would not have to deal with all these hassle. But why not prepare for the worst? Anyway, My best wishes. Good luck.