For words that only have three letters, there is no 4th letter. As an example with the word “incorporate”, there isn't any much more letters Later on and therefore should be the word "increase". The word “addict” is within the BIP39 wordlist but you might have utilized “addi” for “addict”. https://toplistar.com/story20668326/the-5-second-trick-for-ledger-seed-phrase-bip39