The Cp value come from Fluent - read https://ansyshelp.ansys.com/account/Secured?returnurl=/Views/Secured/corp/v231/en/flu_ug/flu_ug_fvdefs.html and will tell you which reference value(s) are used. How to change those is covered in the materials SRP and I have already mentioned.
You are navigating away from the AIS Discovery experience