They are not being harsh or strict, they simply have grade requirements that you did not meet, and you missed by quite a long way. Their suggestion that you get another 4 good grade Highers is probably because they do not rate Music or Computing, and possibly Business too, as sufficiently academic subjects.
If you really want to go there, you will have to take a gap year and retake your Highers, in more academic subjects. What subject are you applying for?
Otherwise get into Clearing and see where you can get a place with the results you already have.