For words that have only three letters, there isn't any 4th letter. For example with the word “increase”, there are no much more letters afterwards and therefore needs to be the word "incorporate". The word “addict” is from the BIP39 wordlist however you might have utilised “addi” for “addict”. A https://pr1bookmarks.com/story20024977/getting-my-bip39-words-to-numbers-to-work