Often times you might want to show some additional information to customers if they live in specific area. Most merchants use this feature to show delivery days or delivery rates to customers.
You can find this setting while configuring your Zip code set. Once you enable this with appropriate message, additional message would get appended to a configured success message.
Each zip code set can have different message.
If you wish to change a success message which appears before this message, you can change it through "Design & Validator" Settings.