Over dediplication

Hello,
I’m a french recent user of PHPlist.
I’ve already send some campagnes.
I create a new list and paste to it our clients list (2579 mail adresses)

I receive the following message
"2579 lignes traitées
741 adresses électroniques importées
1836 doublons
2 non valide
44 adresses ont été mises sur liste noire et n’ont pas été abonnées à la liste"

When I deduplicate our file, I found 82 duplicate adresses.
How can PHPlist found 1836 duplicate adresses ???

looking forward to tour reply,
best wishes
Roland

@RolandGautier I think that the 1,836 are email addresses which were already in phplist, not duplicated in your input file.