In similar context, can I understand "you're telling me" as "you mean"?
"You're telling me" is often used to confirm that you understand everything that someone told you correctly. In that case it can be that you heard and understood what the person said but now you want to confirm your understanding. It can also be that you think you understood what the other person said, but you're not sure, so you want to confirm. Because of this there are some situations where you could replace "you're telling me" with "you mean". However, "you mean" has nuance like the person wasn't saying something exactly but they implied it, whereas "you're telling me" has the nuance that this is exactly what the person said. So they cannot always be interchanged. Ex: A: Well, I guess I have to go to summer classes. B: Wait! You mean you failed your exam? Ex: A: Even though I studied and studied and did my best I still didn't get a high grade. So I have to go to summer classes. B: Wait! You're telling me you failed your exam!