For words that have only three letters, there is no 4th letter. For example with the word “increase”, there isn't any much more letters afterwards and thus have to be the word "include". The word “addict” is in the BIP39 wordlist but you might have made use of “addi” for https://www.slideserve.com/lewarthbfp/bip39-word-list-explained-your-essential-source-for-creating-secure-purses-in-t