Emergency qestions about 485,pls help!

I am preparing for my I-485 application (with my hu*****and). I just found out that one of my I-20's entry date is wrong,(it is supposed to be 2001 but it is 2003). I applied a student visa in Mexico in 2001 and the immigration officer put the wrong date on the I-20 form and the passport when I passed the board. Then I used this visa go back to china for a month (in 2001). When I came back from China, I got the new I-94 card but no stamp on the I-20. My quesiton is do I have to the copy of this I-20? (I have several I-20s, one is from the first entry to U.S, one is for trasferring school, one is SEVIS one and another one is for applying for OPT). Or if I have to submmit this one, do I need to attach a letter to explain this. Thank you very much!!!