This is Usenet, not p2p/torrents.
Altbinz does not need to simultaneously download multiple collections.
Collections will be downloaded one after the other.
When one collection is done, the next will start
There's no point in downloading several collections at the same time, because the peak achievable bandwidth is not relevant to each collection individually (as it is in torrents),
peak bandwidth speed is relevant only to your physical connection speed / the available/free bandwidth on that physical link, + how many threads (connections) to the Usenet server you have open.