For words that have only three letters, there's no 4th letter. For example with the word “incorporate”, there are no much more letters Later on and therefore needs to be the word "increase". The word “addict” is from the BIP39 wordlist however , you might have made use of “addi” https://bookmarkingace.com/story19607076/ledger-seed-phrase-bip39-no-further-a-mystery