Q. Where did the $4000 come from, and why is it not 0?
A. $4000 is the amount of tuition needed to claim the maximum American Opportunity Credit (AOC $2500). It takes $10,000 of tuition to get the maximum Lifetime Learning Credit (LLC $2000).
The AOC is only available to undergrads, so it is the most commonly claimed credit. So, more users need to change the $10,000 to $4000 than need to change it to 0 (because they don't qualify at all).
