For words that have only three letters, there is absolutely no 4th letter. By way of example with the word “increase”, there aren't any much more letters Later on and thus must be the word "increase". The word “addict” is during the BIP39 wordlist however , you might have employed https://bookmarkingquest.com/story18744508/an-unbiased-view-of-bip39-seed-phrase-github