These “grades” are very subjective based on which quotes they decided to cherry pick.
The website does ask for corrections:
WHAT ARE WE MISSING? Are you aware of statements by a candidate that we don't have, especially if they suggest a different stance than what we show? If so, send url links to us at: elections2016@numbersusa.com
In the interest of accuracy, you might send them your cites. I'd rather base my judgments on true and correct information.