For words that have only 3 letters, there is no 4th letter. One example is with the word “include”, there isn't any a lot more letters afterwards and therefore must be the word "insert". The word “addict” is from the BIP39 wordlist however you might have applied “addi” for “addict”. https://bookmarkeasier.com/story18764940/examine-this-report-on-bip39-mnemonic-phrase-tool