I've been looking through the postings and can't find the answer to my question -- how do I properly count the number of continents for a DONE?

Here's my itinerary: YUL GVA SYD LAX NYC YUL.

I thought it was a three continents RTW but a colleague tells me that it is four. BA's RTW desk at first said three and then put me on hold and said it was four.

Can someone provide a quick correct answer?

Thanks in advance!