Across all clients, 7-8% of interactions result in an IDK ("I Don't Know") response. Having less than 10% of your chatbot's interactions result in an IDK response is considered successful. 

Although the chatbot is always learning and you should see a gradual decrease in the frequency of IDK responses over time, you will likely never be able to eliminate all of them; about 5% of questions/comments the chatbot receives are undecipherable or about topics that the chatbot is not designed to answer.