For words that only have 3 letters, there is no 4th letter. For example with the word “increase”, there aren't any additional letters Later on and so has to be the word "increase". The word “addict” is within the BIP39 wordlist however, you would have employed “addi” for “addict”. Unlock https://geniusbookmarks.com/story19015864/bip39-seed-phrase-mnemonics-generator-an-overview