only the 10 best units do count towards your UAI, so thats why many people have a back up subject just incase they dont do too well in it
all in all, no the 2 unit maths subject will not really affect your UAI at all
well, im doing majourly bad in another subject so that 4 sure wont count, and therefore 1unit of maths will count, which is also reli crappy...so, that 1unit of maths included in my top 10, wont majourly effect me rite....??
but if you're doing 12 subjects, 10 of your units will have to count, which leaves another 2 unit that doesnt count...not 4
itll be best if you list your subjects