Conditonal Formating Excel 2007 - Duplicate Values
 

I am using the Duplicate values identifier of conditional formating in Excel
2007. I want to highlite cells if 16 characters number (text Format) appears
more than once. The function works well for first 15 characters but doesn't
differentiate the last characters.
As example: conditional formating sees this text format number
"6001573308858004" to be a duplicate of "6001573308858008" although last
characterer is different. Though, it sees the difference between
"6001573308858004" and "6001573308858014".

I suspect that function checks only first 15 characters. Can somebody confirm?

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Thanks very much.