Churchill, I am fairly certain that the Dean of Admission was mistaken…or that you misunderstood him. He was referring to the total number of Chicago graduates currently enrolled at Yale Law school, not to the percentage of Yale Law School students that are Chicago graduates.
http://bulletin.printer.yale.edu/pdffiles/law.pdf
If you scroll down to pages 166-168, you will see what I mean. There are currently 656 Yale Law students. Of those, 10 are Chicago graduates. For a non-East Coast school, 10 is excellent mind you. Only Stanford (19) and Cal (16) have more. Michigan, Northwestern, UCLA and WUSTL all have 6-7. A couple of years ago, Michigan had 11, but the last two years must have been thin! 
Harvard and Yale have 65 and 69 graduates enrolled at Yale Law school respectively. Princeton has 37. Columbia has 30 and Brown has 22. No other university has more than 19, which represents less than 3% of the Yale Law school class.
It is doubtful that 2017 is any different. Like I said, it is more likely that he was referring to the total number of Chicago graduates at Yale Law school, which is 10, or slightly under 2% of the total.
And I do not think the dean was referring to the class of 2017 either since the application deadline was February 28, and most decisions have not even yet been made (they are usually made in mid-late April).
But while we are on the topic of Yale educated deans at Chicago, perhaps you should trust the judgement of Gerhard Casper, Yale alumnus, and dean of the Chicago Law school from 1979-1987. He then went on to be president of Stanford University from 1992-2000. In 1996, he wrote a letter to the new editor of the US News, critiquing the methodology of its undergraduate ranking. Below is a quote directly from his letter:
“I am extremely skeptical that the quality of a university - any more than the quality of a magazine - can be measured statistically. However, even if it can, the producers of the U.S. News rankings remain far from discovering the method. Let me offer as prima facie evidence two great public universities: the University of Michigan-Ann Arbor and the University of California-Berkeley. These clearly are among the very best universities in America - one could make a strong argument for either in the top half-dozen. Yet, in the last three years, the U.S. News formula has assigned them ranks that lead many readers to infer that they are second rate: Michigan 21-24-24, and Berkeley 23-26-27.”
https://web.stanford.edu/dept/pres-provost/president/speeches/961206gcfallow.html
You may know better than Dr. Casper, but he seems to think that Michigan and Cal are peers, and that they are both among the best undergraduate institutions in the country…arguably among the “top half-dozen”.