For words that only have three letters, there is no 4th letter. Such as with the word “increase”, there aren't any much more letters afterwards and so must be the word "increase". The word “addict” is from the BIP39 wordlist however, you might have made use of “addi” for “addict”. https://sirketlist.com/story20552847/ledger-seed-phrase-bip39-no-further-a-mystery