For words that only have three letters, there's no 4th letter. For instance with the word “increase”, there aren't any more letters Later on and so needs to be the word "incorporate". The word “addict” is from the BIP39 wordlist but you would have applied “addi” for “addict”. When you https://bookmarkingace.com/story18862090/the-fact-about-valid-bip39-seed-phrase-that-no-one-is-suggesting