For words that only have 3 letters, there is no 4th letter. One example is with the word “insert”, there isn't any far more letters Later on and therefore has to be the word "increase". The word “addict” is during the BIP39 wordlist however , you would have utilised “addi” https://mediajx.com/story21474172/bip39-phrase-generator-can-be-fun-for-anyone