For words that only have 3 letters, there is no 4th letter. By way of example with the word “increase”, there isn't any much more letters Later on and so need to be the word "increase". The word “addict” is from the BIP39 wordlist but you would've applied “addi” for https://olivebookmarks.com/story19119705/a-secret-weapon-for-bip39-words-to-numbers