I played around with SAM about what u said and I found that getting 0 in 4u and having 3u count for 2u is worse then doing well in 2u and getting 90 in 3u.
EXAMPLE 1: Not doing 4u and getting 93+ in 2u
If u did 3u maths, eng adv, phys, chem, eco, got 90 in all
getting 93 in 2u SAM UAI...