Excel 2007 :: Can't Find Duplicates In FedEx Tracking Numbers?

We were looking at a list of about 100 FedEx tracking numbers, each 30 characters in length, in an otherwise blank Excel spreadsheet. All tracking numbers in column A.

I used the Conditional Formatting - Highlight Duplicates feature to find any duplicate tracking numbers. It highlighted numerous. We sorted the column smallest to largest to look at two duplicates back to back, but found that there were actually no duplicates. Excel was highlighting values that had the *first 25* characters the same, but it didn't matter what the remaining characters were. For example:

1234567890123456789012345XXXXX and
1234567890123456789012345YYYYY

were highlighted as duplicates of each other.

Excel only looks at the first 25 characters when analyzing duplicates (at least in this specific function). That in and of itself blows my mind. Tracking numbers seem like an abundantly common type of data, and to think that Excel would fail to analyze them in such a simple manner seems impossible to me.

It gets slightly more confusing though. If you back a character off the end of the values, it NO LONGER sees them as duplicates. So...

1234567890123456789012345XXXX and
1234567890123456789012345YYYYY

are NOT highlighted as duplicates while

1234567890123456789012345XXXXX and
1234567890123456789012345YYYYY

ARE highlighted as duplicates. So there's some funny business going on about values of the same character length. Maybe Excel first looks at character length before analyzing specific characters. If length doesn't match, it doesn't even bother to analyze specific character values. That seems like a very strange programming choice though.