Celeborn the Wise's first ability has you scry 1 just once whenever you attack with one or more Elves, no matter how many Elves you attack with and no matter how many players you attack.

Celeborn the Wise's last ability cares about the number of cards you actually looked at. For example, if you were supposed to scry 3 but only had two cards in your library, Celeborn would get +2/+2.