Theres Absolutely no impact...
As long as you did your FP before INS began processing for your RD date , there is no impact. Since you have already done this , dont worry about it.
Actually look at it this way... you will not have to redo your FP after 15 months (=20Aug2004 in your case)! because by that time your case would be long since approved.
Early FP <> Early GC
Late FP <> Late GC