I was there on Oct.31. They interview around 60 people a day. The writing topic for that day was "what's the most influential teacher in your life and why?" hope it helps 🙂
P.S. they don't really care about the writing. They only gave 15 mins. Somebody wrote just a little paragraph and somebody wrote alot. doesn't really matter. no stress.
San Antonio's essay doesn't affect your acceptance. At least that's what the lady said. It's just a survey evaluating your opinion of the interview. The question was "what was the most reassuring thing that you experienced today?"