I'm surprised that they split the maths/aptitude tests and group exercises/interview over two assessment days, unless they are charging for those days separately. From what I know, the maths test takes about twenty minutes, followed by the aptitude tests which can't be any more than an hour. Can't see the reasoning tests taking any more than a couple of hours combined. Group exercises I reckon should be about an hour maximum too.
Could easily put that into a morning followed by an afternoon of interviews.