For words that only have 3 letters, there is not any 4th letter. As an example with the word “include”, there won't be any more letters Later on and so need to be the word "add". The word “addict” is during the BIP39 wordlist but you might have utilized “addi” https://mysocialquiz.com/story4482220/ledger-seed-phrase-bip39-no-further-a-mystery