What has made John so surprised?

M: Hello. Is this the registration office?
W: Yes. This is Kate speaking. How can I help you?
M: Well, I have a slight problem here. (4) I have been in Chemistry 302B class for a month, and today Prof. Anderson told me I wasn’t registered in his latest class list. I thought all the while I was registered in his class and this really comes as a surprise.
W: Well, why don’t you give me your student ID and I’ll just check to see if you are officially registered.
M: 37754.
W: Just a minute. And you are John Ashton, right?
M: Yes, that’s me.
W: John, the computer shows that you are registered in Chemistry 302A and that’s Dr. Bolton’s class. Perhaps you have mixed up the two.
M: Oh no, I thought I’d made a switch from Bolton to Anderson. How did this confusion occur? I dropped Bolton’s class and switched to Anderson’s in the first week. I still have the add/drop form with me.
W: In that case, (6) I suggest you come to the registration office with the add/drop form and we’ll try to sort it out for you. (5) I don’t rule out there could have been a mistake that occurred during the add/drop process.
M: I’ll be there first thing in the morning to sort out this mess. You know, I wouldn’t want to switch professors when I’m now half way through.
W: I can understand that. See you tomorrow.