For words that only have three letters, there is no 4th letter. As an example with the word “add”, there isn't any extra letters Later on and so must be the word "incorporate". The word “addict” is inside the BIP39 wordlist but you might have employed “addi” for “addict”. You https://thefairlist.com/story9229098/examine-this-report-on-bip39-passphrase