Retirement tax questions

That is the publication and page I have been reading.  I swear I will get this. I am determined.

 

A excess made *for* 2019 that is returned *in* 2019 would have a code 8.  That is what I have however its on the 2020 - 1099-R Box 7 code 8 and their letter said it was for the 2019 401K excess contribution .   What date is used  for "returned *in* 2019"  by -  to determine the code P or code 8.  Do they go by December 31, 2019 it has to be returned to me OR April 15, 2020 by the 2019 filing deadline? And I never received anything in the current or past with a code P.