For words that have only 3 letters, there is no 4th letter. For example with the word “increase”, there aren't any a lot more letters Later on and so need to be the word "increase". The word “addict” is during the BIP39 wordlist however, you might have used “addi” for https://socialmediastore.net/story19458804/the-2-minute-rule-for-bip39-all-words