Handling College Refund for 529 account

in Oct 2019, I paid room/boarding of $12000 for entire year (part 2019 and part 2020) for my kid. 

My kid was in the dorm till March and then return home due to COVID.  In May2020, I received refund of $4800 from the college. Technically, i should have re-contributed this amount to 529 account within 60 days, but i did not know.

So, might be slapped taxes + 10% penalty on $4800.

 

However (my question), since I continued to make payments in 2020 for Tuition and next year 2021 room boarding, I really dont have to pay the penalty.... since I am spending this "$4800" for eligible expenses within 2020.

 

Am I missing something? Is there anything I can do in last two weeks of Dec to avoid penalty?