For words that have only 3 letters, there's no 4th letter. Such as with the word “increase”, there won't be any far more letters Later on and therefore has to be the word "insert". The word “addict” is while in the BIP39 wordlist however , you would have made use https://crossbookmark.com/story18926563/bip39-seed-phrase-mnemonics-generator-an-overview