The AOTC is 100% of the first $2000 of tuition and 25% of the 2nd $2000. So, a maximum of $2500 per student.
It is only 40% refundable. The most likely explanation is that you only had a tax liability of $1714 (line 18 of form 1040). The non refundable portion of the AOTC will be shown on line 20 of form 1040 (transferred from line 3 of Schedule 3 and form 8863). The $2000 refundable portion ($1000 per student) will be shown on line 29 of form 1040.