'Three' denotes fullness, and 'a third,' not full.

(References: Arcana Coelestia 2788 [1-13])

'A whale,' as in Jeremiah 51:34, signifies people who possess the universal aspects of the knowledges of faith, as known, and apply them to evil purposes. 'Whales,' or 'great fishes,' are sometimes mentioned in the prophets, and are used to signify the universal aspects of knowledges

(References: Arcana Coelestia 42)