For words that have only 3 letters, there is not any 4th letter. One example is with the word “increase”, there isn't any far more letters Later on and so should be the word "include". The word “addict” is in the BIP39 wordlist however , you would have applied “addi” https://captainbookmark.com/story18904576/examine-this-report-on-bip39-mnemonic-phrase-tool