American Opportunity Credit requires you to be in (a) 4 years of post secondary education -- not grad school; (b) have a Tax id ; (c) no felony and a bunch of other requirements.
You came here on F-1 in 2012 and therefore started counting days present in 2017. Therefore I suspect that you are either in grad school in 2018 or post doc in 2018. Therefore you are not eligible for American Opportunity Credit --- your 1098-T should have the grand school box checked -- perhaps you did not enter that and TurboTax therefore assumed you are an under grad.
Does this answer your query ?
