nice of you to create a table with markdown, but it would be also easier to see the actual records without markdown table - just the markdown code tags.
I'm listing it here - modify if the actual data looks different:
A 2020-06-09 7:12:22
A 2020-06-03 18:26:07
A 2020-05-16 21:52:12
A 2020-05-16 22:37:18
B 2020-05-19 3:11:05
C 2020-06-06 21:14:44
C 2020-06-06 21:14:44
C 2020-06-06 21:14:46
C 2020-06-06 21:14:48
C 2020-06-06 22:16:50
C 2020-06-06 22:16:55
C 2020-06-06 0:16:50
C 2020-06-06 1:16:50
C 2020-06-12 22:20:00
C 2020-06-12 22:20:00
C 2020-06-12 22:20:03
C 2020-06-12 22:20:03
C 2020-06-12 22:20:04
D 2020-06-03 23:26:07
D 2020-05-16 21:52:12
D 2020-05-16 22:37:18
D 2020-05-16 23:39:18
Have you tried anything on your end and if so where exactly are you stuck?
There's a slew of similar questions in these forums and on the web dialing with "uniqueness" of one sort or the other. Have you searched anywhere for hints?
Usually it's a one-liner and it's in this case as well...