Good point, Albator.
I did consider All Of You but put it in the high 100k's bracket. Although it was #1 in Spain singles sales there are quite low. I had Grmany/ France/ Italy/ Netherlands about 260k. Canada/ Australia/ NZ/ Belgium/ Austria wouldn't be that much . Maybe Scandinavian and other countries in Europe would collectively have amounted to a respectable total.
But what I hadn't considered was the South American market which would have been lucrative for JI.
I don't think Diana was ever a big seller there although somewhat strngely her Stop Look Listen duet with Marvin Gaye was #1 in Brazil but I really don't know much about that Continent's market.
But I think you may be right about All Of You being a million seller.