For words that only have 3 letters, there isn't a 4th letter. For example with the word “increase”, there are no a lot more letters afterwards and therefore have to be the word "include". The word “addict” is in the BIP39 wordlist but you might have utilized “addi” for “addict”. https://kingslists.com/story20727850/detailed-notes-on-copyright-wallet-seed-phrase-out-of-bip39