Hi,
1 Karat is purity by mass
X = Mg / Mm where X is the Karat rating of the material, Mg is the mass of pure gold in the material, and Mm is the total mass of the material. So I believe you made a mistake: The purest is 24 Karat..... 24 Karat is 999 pure and 14 Karat is 585 pure (all out of 1000). Hope it's clear.
Best regards,