Is this some kind of public school math? By my calculations, slightly less than 61% would do it.
Here's how I figure it. Subtract the current margin of victory from the number of uncounted ballots, and split the remainder. That gives you how many the current winner needs to stay ahead.
So for Dino to win, he needs to beat (573-121)/2, which is 226, or about 40% of 573.