Translation:My grandfather's name is not Aamir but Raj.
I'm not sure either, but I definitely learned something from this question. The way it makes more sense to me is if its separated into two sentences- 1. Take out the राज = मेरे नाना का नाम आमिर नहीं है (i.e. My grandfathers name is not Amir), 2. [ooska naam] राज है (i.e. His name is Raj)
My understanding is that commas are not part of traditional Hindi punctuation. As a matter of fact, I think the only punctuation mark that is traditional to the language is the | at the end of the sentence. However, commas, question marks and such are being used these days. This course seems to be teaching very traditional Hindi (note the pronunciation of यह for example).