I think your calculations are reasonable. We probably won’t know the yield rate for sure until the Common Data is released in the fall. A couple of points:
Rick Shaw said in the spring that the goal for the Class of 2020 was 1,730 students. I don’t know why just a month or so later he would go 38 higher. On the other hand, Shaw does have a record of admitting and then enrolling too many students. My guess (and it is only a guess) is that admissions officers push hard for their kids and Shaw doesn’t say no as often as he should.
Last year 15 transfer students enrolled.
This year according to CC some kids were admitted off the waiting list. It appears that this activity occurred soon after May 1 and has been quiet for some time. 20-30 off the wait list seems reasonable although it is higher than in prior years.
Whether the yield rate is 80%, 82%, or 85%, Stanford is one tough place to get into.