The AOTC is only 40% refundable. The other 60% can only be used to offset an actual tax liability. So, the 40% refundable portion ($1000) will show on line 28 of form 1040. Because your tax liability is low, you get something less than $1500 for the non refundable portion of the AOTC. See line 19 of form 8863.
