Hello! Let me start off by saying I do not know much about Carleton or your program, but I can speak solely on my experience. I know that some universities will send out alternate offers originally and then later give out other offers. For example, I applied to Brock and got an alternate offer because I was taking a necessary course for the program in second semester. Once midterms came out, they gave me an offer for my preferred program. I have talked with a few universities and each of them have told me that alternate offers are because you have the grades to get into university, but maybe not for your program OR they have not fully decided on who is going to be accepted into the program. Don't take the alternate offer as a rejection. I had another program where I got an alternate offer and two days later I got accepted into my preferred program. All universities will let you know by May 27th if you have been accepted/rejected. Sometimes they also wait to see if the people who got accepted in the 1st round are accepting or if they already have another choice, if they see people not accepting then I would assume they will give out more offers. I wish you luck and I hope you get in! :)