First, check the text which is setup on the confirmation page. If after checking this text, you don't find anything awry, the behavior is likely browser related. 

Check setup of confirmation page
The exact steps will vary based on the type of form you're editing.
  • Attempt the form in another browser
  • Here is a 3rd party link on how to clear cache: Note: We provide links to third-party websites in an effort to help you resolve your issue. We are not responsible for the information on third-party websites and we cannot assist with implementing resolutions from these websites.
Additional Resources: