COUNTIF showing matches that don't really match

I am helping to solve this thread: https://www.excelforum.com/excel-for...ml#post4901325

There is an oddity in here that I have boiled down to the attached file. There are values that consist of strings of 19 digits, prefaced with ' to indicate they are text. COUNTIF is considering two strings to match but they are totally different.

My educated guess is that COUNTIF is looking at these strings as if they were integers, and lopping off the precision that is not supported by Excel (Excel maintains only the most significant 15 digits). When I change the 15th digit, COUNTIF no longer finds a match.

The point of this exercise is to find duplicates in the list, but Excel is showing false duplicates. Looking for a way to find true duplicates.

I tried a suggestion trimming the 1st 4 digits