For words that have only 3 letters, there is no 4th letter. As an example with the word “increase”, there aren't any more letters Later on and therefore need to be the word "insert". The word “addict” is during the BIP39 wordlist however , you might have utilized “addi” for https://ticketsbookmarks.com/story18724645/little-known-facts-about-bip39-seed-phrase-list