For words that only have three letters, there is no 4th letter. For example with the word “add”, there are no additional letters afterwards and thus must be the word "include". The word “addict” is in the BIP39 wordlist however , you might have employed “addi” for “addict”. bip39-phrase.com is https://pageoftoday.com/story4254149/examine-this-report-on-bip39-passphrase