It was about 82 % no matter how you figure it out. If you add up all of Vinatieri's field goal percentages for each of the nine years he played for the Patriots and average them out you get about 82.3 % but if you add up all of his makes (243) and divide them by the number of attempts (269) you get 82.1 %. This is pretty close to his overall career field goal percentage of 82.0 %. Doing the math for you, if he attempted 269 field goals while he was a Patriot and made 243 of them, he missed 53 as a Patriot.
Hope this helped.
Edit: I love how I come back to this thread two days later to cite my source and find that even though I've given first and the only serious answer to the question, I have two thumbs down and no thumbs up. Good stuff.
ESPN.com's Adam Vinatieri Profile & Career Statistics