TravelTalkOnline Forums Travel and Vacation Forums St. Maarten - St. Martin Entry Form, origin & flight #

I think the form reads "originating" not connecting, so in your case it would be the first leg of flight (Milwaukee). We don't live in MA but we'll fly out of BOS so that's what I listed along with that flight #.
But, then our flight is direct from BOS.

So perhaps SXMScubaman is correct in his posting. Also, he's seldom wrong in his advice.