For words that have only three letters, there isn't a 4th letter. By way of example with the word “incorporate”, there isn't any a lot more letters afterwards and thus should be the word "add". The word “addict” is in the BIP39 wordlist however , you would have used “addi” https://madesocials.com/story4617450/ledger-seed-phrase-bip39-no-further-a-mystery