For words that only have three letters, there isn't any 4th letter. By way of example with the word “incorporate”, there aren't any more letters Later on and therefore have to be the word "include". The word “addict” is in the BIP39 wordlist but you might have utilised “addi” for https://tvsocialnews.com/story5135381/getting-my-bip39-words-to-numbers-to-work