This morning I got into UCI’s 2020 Math Explr Program and they addressed me a letter (with my name) for me to accept the position. Then, about 20 minutes later, they had sent me a rejection email. Does this mean I got rejected?
Call or email admissions and ask. No one here will be able to say for sure. These mistakes do happen in both directions, though.
Actually, I got accepted in the end! It was a mistake on their part, so I guess everything worked out in the end 