I recall a blog post where someone remarked that "7 is really a 3". Precisely because of Dunning-Kruger: people who don't know how big the field is just say 7 because it seems reasonably high and yet doesn't imply mastery.
That'd imply that game-theoretically, the right answer is 8. ;-) Enough to tell the interviewer that you've gotten past 7, yet not so high to make them think that you think you know everything.
(Personally, I've taken to saying "Judge for yourself" and listing my accomplishments. That's what they're really interested in, they're going to do it anyway, and this way I show enough confidence in my own abilities that I'm willing to let others judge them.)
That'd imply that game-theoretically, the right answer is 8. ;-) Enough to tell the interviewer that you've gotten past 7, yet not so high to make them think that you think you know everything.
(Personally, I've taken to saying "Judge for yourself" and listing my accomplishments. That's what they're really interested in, they're going to do it anyway, and this way I show enough confidence in my own abilities that I'm willing to let others judge them.)