For words that have only 3 letters, there isn't any 4th letter. Such as with the word “add”, there isn't any a lot more letters Later on and therefore have to be the word "add". The word “addict” is from the BIP39 wordlist however you would've utilized “addi” for “addict”. https://bookmarkforest.com/story18780921/the-5-second-trick-for-ledger-seed-phrase-bip39