Indeed, you could easily set it to 10gb, it will not use that space but you do get ~200% of the usual points for that..
UD supports multiple projects, but currently the ligandfit project is running.
This project does not use much HD space as it uses cpu power.
Other projects concern internet speed testing utilize lots of bandwith, therefore you get points on each factor.
But you can select to which projects your willing to participate on their website..
(don't know any projects which uses lot's of HD space though
)