For words that have only 3 letters, there is not any 4th letter. As an example with the word “add”, there won't be any a lot more letters Later on and thus need to be the word "include". The word “addict” is from the BIP39 wordlist however you might have https://ticketsbookmarks.com/story18784964/a-secret-weapon-for-bip39-words-to-numbers