For words that only have 3 letters, there isn't any 4th letter. For example with the word “increase”, there aren't any more letters Later on and so needs to be the word "include". The word “addict” is in the BIP39 wordlist however, you would have made use of “addi” for https://pr7bookmark.com/story19047779/examine-this-report-on-bip39-mnemonic-phrase-tool