How concerned should I be?

The error would not bother me, people dont roll back the miles only 500. If it was infact driving 30,000 miles and someone rolled it back, they would have for sure not made the mistake of going to far. Its a simple error, no ones going to care.

Last thing to check, no high perf tire last more than 10,000 miles, what the dot date on the tires?

 

I would say thats proof enough of actuate mileage. if the car was driven any substantial amount it would have newer tires from 2012-2014 IMO

 

So we now know 5 years of no miles. I would consider a thorough check-up and even a major service, especially because it has not been driven.

The F355 is a great car and nearly all of its problems have known, relatively permanent solutions.