For words that only have 3 letters, there isn't any 4th letter. For instance with the word “add”, there are no a lot more letters afterwards and therefore should be the word "insert". The word “addict” is while in the BIP39 wordlist however you would have applied “addi” for “addict”. https://open.substack.com/pub/jaidenqrel955/p/unlocking-the-power-of-bip39-how?r=54uq0h&utm_campaign=post&utm_medium=web&showWelcomeOnShare=true