It's not going to hurt if you want to try and resubmit it via mail (for piece of mind). But, the likely end result is that the IRS is going to discard the note and when they go to process the extension it will get rejected because one has already been filed under your SSN. Like I said above, the form itself isn't designed to be corrected - the normal path to correct it is to just file your tax return with the correct information.
