PJiang and Xiaobaitu Please Help!!!!!!!!

Hi

I just found out there is a huge problem in my I-485 application. my employment letter said I was employed Feb 7th(could be mistake by HR, But I already quit this Job and no chance to ask them to change it back),2007 but my OPT start with Feb 11th, 2007. Does that mean I was illegally working for 4 days? How bad it could be?? Please Help!!!_(u) _:'(