回複：how many reference letter do I

Your lawyer sounds crappy or you misunderstood what he/she said to you. You better prepare six or more letters from both inside cycle and outside cycle including govermental officer (if you are in NIW).
Responding to ITD is equivalent to making another petition regarding cover letter and recommendations etc. However, if you win, you win all, simply becaue you have a chance to re-convince the INS officer for the second time, and much better strike. Good luck.