For words that have only 3 letters, there's no 4th letter. For instance with the word “increase”, there won't be any much more letters Later on and therefore must be the word "insert". The word “addict” is within the BIP39 wordlist but you might have utilized “addi” for “addict”. Mnemonic https://socialdosa.com/story8669182/a-review-of-bip39-passphrase