The only thing I would say on the dreaded cube test is that it is pretty much designed to make you feel as though it has gone badly. That's why there are so many questions in such a short space of time; it tries to make you flap and see how you cope.
I've done similar things like it before and each time you come out semi-baffled.
I'd think that as long as your accuracy (i.e. the ones you answered you got right) is pretty good then 25 shouldn't be too bad a number.