For words that only have three letters, there is not any 4th letter. As an example with the word “increase”, there won't be any additional letters Later on and therefore should be the word "insert". The word “addict” is in the BIP39 wordlist however you might have utilized “addi” for https://social-medialink.com/story4086331/ledger-seed-phrase-bip39-no-further-a-mystery