For words that have only 3 letters, there's no 4th letter. One example is with the word “include”, there won't be any a lot more letters afterwards and therefore should be the word "insert". The word “addict” is inside the BIP39 wordlist but you would've applied “addi” for “addict”. Several https://nybookmark.com/story20438239/examine-this-report-on-bip39-mnemonic-phrase-tool