A '6 unit award' is equivalent to an A-level. So, your General Studies A-level is acceptable because it's one of your 3 A-levels.
You've got the preferred number of A-levels (3), because General Studies is counted.
Your grades for a B, C & D at A-level are, respectively, worth 100, 80 and 60 UCAS points, so you've got 240 acceptable points solely from those qualifications. Your AS results also count towards your total acceptable points because they're offered alongside points obtained from A-levels.
So, you've met the requirements purely on the basis of your A-level results. The extra 50 points from your AS qualifications will help you towards 'preferred candidate' status if the course is over-subscribed.
Chris