For words that have only 3 letters, there isn't a 4th letter. By way of example with the word “add”, there isn't any much more letters Later on and therefore should be the word "include". The word “addict” is during the BIP39 wordlist however, you would've utilized “addi” for “addict”. https://bookmarkpagerank.com/story18816320/ledger-seed-phrase-bip39-no-further-a-mystery