For words that only have 3 letters, there is not any 4th letter. Such as with the word “include”, there won't be any a lot more letters afterwards and therefore needs to be the word "add". The word “addict” is within the BIP39 wordlist however you would've applied “addi” for https://bookmarkstown.com/story19247272/getting-my-bip39-words-to-numbers-to-work