For words that have only three letters, there is not any 4th letter. For example with the word “increase”, there aren't any far more letters Later on and therefore should be the word "insert". The word “addict” is from the BIP39 wordlist however, you would've utilised “addi” for “addict”. Meticulously https://esocialmall.com/story4211593/facts-about-bip39-seed-phrase-word-list-revealed