That map does not really look right. Southwest from the Kingdom of Hungary it shows a "country" called Hermann of Celje. Well, that was this guy: http://en.wikipedia.org/wiki/Hermann_II_of_Celje

The point is, that wasn't a country. This was a man. Herrmann was an Austrian count, who own plenty of land in German-Roman Empire and in the Kingdom of Hungary. He was a vassal of, on the Hungarian side, King Sigismund, and on the Austrian side, as vassal of the Habsburgs: http://en.wikipedia.org/wiki/Count_of_Celje

So it was simply the lands that happened to be owned by a count, nothing more really.

Anyway, my point is that that the map has way too many borders, it does not show what is a independent kingdom, what is not, although I admit that it would be difficult to show it, as the transnational lines of vassalhood did not mean cultural unity. It is sometimes meaningful to show the borders of a territory that is not independent in vassalhood but has its own culture. But for example these lands had neither their own cultural character nor independence.

So I have no idea why the author thought ol' Hermann is a country now.

(Source: a monograph about King Sigismund, published in Hungarian as Tört Királytükör, by László Passuth).