For words that have only 3 letters, there is no 4th letter. For example with the word “insert”, there won't be any a lot more letters afterwards and therefore must be the word "add". The word “addict” is in the BIP39 wordlist however , you would have utilised “addi” for https://bookmarkswing.com/story20445101/little-known-facts-about-bip39-seed-phrase-list