You would need paperwork from the DMV stating that the mileage is accurate, it would have to be signed by the seller and be notarized as well. If you already signed it and turned it in... too late.
Yes it will not matter unless you go to sell it. But you will never be able to sell it and be able to accurately represent the miles and no dealer will ever give you more than the bare minimum if at all for trade.
2000 Mustang GT Steeda #0048
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.