For words that have only 3 letters, there is no 4th letter. As an example with the word “increase”, there won't be any more letters Later on and thus needs to be the word "insert". The word “addict” is from the BIP39 wordlist however, you might have utilized “addi” for https://classifylist.com/story20738119/the-greatest-guide-to-seed-phrase-bip39