Finding Duplicate Values in a Col,

I have these values in a col A & B.
And I applied this formulae in col B to find duplicates.
It is not deducting the last 3 or 4 digits & showing as duplicates, whereas it is not a duplicate.

=IF(COUNTIF($S$2:S4489,S4489)>1,"d","u")


362971881060091707 u
362971881060091708 d
362971881060116087 u
362971884070003809 u
362972161060074451 u
362972881060075192 u
362972881060085841 u
362973151060096917 u
362973151070001681 u
362973151070014216 u
362973151070014275 d
362973151070014541 d
362973151070014683 d
362973151070030576 u
362973151070030743 d
362973151070043480 u

Make yourself a little test spreadsheet and put 10 single digit numbers in col A, making sure some are duplicates. Put your formula in Column B, dragging it down a further 9 rows. Does it work perfectly? If it does, some of the numbers in your real list may be text, or may have leading or trailing blanks. This is easily checked with a pivot table - look for two apparently identical numbers counted separately.