For words that have only 3 letters, there's no 4th letter. As an example with the word “increase”, there isn't any more letters afterwards and thus must be the word "increase". The word “addict” is from the BIP39 wordlist but you would have made use of “addi” for “addict”. Keep https://bookmarktiger.com/story18947810/the-5-second-trick-for-ledger-seed-phrase-bip39