For words that only have 3 letters, there is no 4th letter. Such as with the word “include”, there are no more letters afterwards and thus must be the word "add". The word “addict” is in the BIP39 wordlist however you would have used “addi” for “addict”. To try to https://active-bookmarks.com/story18893113/a-secret-weapon-for-bip39-words-to-numbers