That tells you how bogus his review was. They didn't really think he was an easily replaced average Joe cog, but they had to fill all their various slots and, I suppose in their view, he should have been happy not to have to been allocated to a worse one.
It's grading on an arbitrary curve, not on merit, "There is no way to tailor the rewards of the team to the actual performance of the team."
70 = You're an average Joe. You're not a bozo, and you're not a rock star, and you're not going to get a promotion soon.