Do i need to file Amendment for 2018 tax return, if have over contributed 401k Amount in 2018, and got amount back from plan administrator

In 2018 i did over contribution to my 401K by $772. So my plan admin started a refund and instead refunded $720 on 31st March. So I have two questions

1) Do i need to file Amendment for 2018 return 

2) What amount should i report. 772 or 720