For words that have only three letters, there isn't a 4th letter. One example is with the word “add”, there are no much more letters afterwards and so need to be the word "add". The word “addict” is in the BIP39 wordlist however , you might have employed “addi” for https://enrollbookmarks.com/story18973990/how-much-you-need-to-expect-you-ll-pay-for-a-good-valid-bip39-seed-phrase