What is the use of a Chilan Berry?

Question

It halves the damage of super-effective normal-type moves. But normal moves are never super-effective. Why does this berry exist?

Comments

No it doesnt the book says super-effective.

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well whatever book youre reading is wrong

Answer 1

It does not half the damage of super effective normal type moves. It halves the effectiveness of normal type moves in general.
Source: http://bulbapedia.bulbagarden.net/wiki/Chilan_berry