It will sound ridiculous to me that they would reject you simply because lower ranked schools rejected you. My suggestion: relax, do some research on that school, and be enthusiastic about your forthcoming conversation.
昨天对方教授给我发了邮件,说“I wanted to let you know that I just signed a letter of acceptance to our PhD program. You should receive it in a few days.”。这个应该是Offer了吧?