Conditional formatting for duplicates

I found another thread with the suggested formula =COUNTIF($D$2:$D,D2)>1

I modified to my document's needs (column c) and it appears to be working. The issue is that when I ctrl+f one of the names being highlighted as a duplicate, there aren't actually 2 instances of the same name.

You can see the search for Kelly is only returning 1 results, but being highlighted as a duplicate

What am I doing wrong here?