Hey!
I don't know the exact answer to your question, but I can tell you my experiences and maybe that will help you a bit.
If you are doing a PhD, I think it makes a lot of sense for them to accept so few people. I have applied for a masters degree. They only accept around 10 people for my cluster. However, the program has multiple clusters (I think five) so there are actually a lot more people being accepted than you assume.
This could be your case. You didn't specify your program so I can't be sure, but I wouldn't worry too much. I would personally really enjoy a small cohort, especially if it was your number one choice.