How to find order refund breakup/details?

When querying the API for order data, one of the fields is refund_total. We have some past orders data we’re analyzing, and though we see a non-zero refund amount for some orders, it’s not clear what the refund was issued for. Is there a way to query deeper into this refund amount? I looked through the REST and legacy APIs but couldn’t figure out anything. Maybe I missed something?