A1. For most filers, it is the amount of your AGI, adjusted gross income, from your tax return. If you file Form 1040 , your MAGI is the AGI on line 11 of that form, modified by adding back any:
A2. In addition to that, there is a phase out of the credit amount between $160,000 and $180,000.
So, if that's not the explanation, see the other rules at:
https://turbotax.intuit.com/tax-tips/college-and-education/what-are-education-tax-credits/L7TuLrVqZ
https://www.irs.gov/Individuals/AOTC
Otherwise, you've answered something wrong in the interview.