For words that only have 3 letters, there is no 4th letter. By way of example with the word “insert”, there won't be any a lot more letters afterwards and thus must be the word "incorporate". The word “addict” is from the BIP39 wordlist however, you would have utilized “addi” https://doctorbookmark.com/story18850424/5-simple-techniques-for-bip39-seed-phrase