For words that have only 3 letters, there isn't any 4th letter. For instance with the word “increase”, there isn't any a lot more letters afterwards and so has to be the word "add". The word “addict” is while in the BIP39 wordlist however, you might have used “addi” for https://atozbookmark.com/story18729078/ledger-seed-phrase-bip39-no-further-a-mystery