It is not random, it was taken from Spotify online store web service, which is not really trivial info to find out (there is a nifty @tatsumo tool for that).
It probably is the countries in which the store sells and where you can buy from.
I have never bought any download album but I know some online stores, like PlayStation Store will only accept credit cards from Japan.
So maybe there are some country checks also for those download albums.
But if we choose to not care, I am not strongly in favour of any choice because, as I said, I am not a digital guy. 