Non-PRO Persian (Farsi) to English Art/Literary Idioms / Maxims / Sayings Idioms

Greetings,

What is the best English equivalent of چطور مگه؟ in this context, please?

خوبی؟
من خوبم، چطور مگه؟

I ask as although my dictionary says that it means ‘Why do you ask’, when I heard this dialogue it sounded more like the equivalent of ‘What the h*ll do you mean by that?’

But I may have misunderstood.

All the best, and many thanks,

Simon