Repaying COVID-19-related distribution to my 401k after plan withholding

Hi there.

 

I took a COVID-19-related distribution from my 401k and am ready to pay it back.  To make the numbers simple, let's say I requested the withdrawal of $100k, but the plan administrator withheld $35,200, ultimately giving me $64,800.  I am now ready to pay this back.

 

Questions:

(1) When paying back my 401k plan, would I pay $64,800 or $100k?  

(2) Do I need to amend 2020 taxes after repayment, or is form 8915-E sufficient?   Amendment seems odd, but is commonly referenced as required in this scenario.

 

I appreciate any insight here.