For words that have only 3 letters, there's no 4th letter. For example with the word “include”, there isn't any extra letters Later on and thus must be the word "insert". The word “addict” is inside the BIP39 wordlist however you would have employed “addi” for “addict”. You signed in https://webookmarks.com/story4362171/bip39-seed-phrase-mnemonics-generator-an-overview