For words that have only 3 letters, there is no 4th letter. Such as with the word “add”, there isn't any a lot more letters Later on and thus need to be the word "add". The word “addict” is from the BIP39 wordlist but you might have used “addi” for https://thebookpage.com/story4295154/the-5-second-trick-for-ledger-seed-phrase-bip39