Freshdesk reports mainly focus on the various metrics that can be calculated from tickets from different sources like the portal, email, social, chat or phone.
These values that are displayed in a report using which you can filter the data presented are the ones that exist in your ticket form or fields that you use within the portal.
The default values of the ticket form cannot be changed in order for it to be reflected so in reports. You could always contact us (support@freshdesk.com) to understand what are the fields you want to report on and we could guide you accordingly.