When a user (even the "Default CMC User") plays media, manually toggles a Title/Episode between Watched or Not Watched, or add/removes a Title to their personal WatchLists, this data is synced from CMC to CCC to update the master database, which in turn is synced back down to all other CMC HTPC's.
If you would like to see this data, in CCC you can open Settings and select the "Reports" tab:
There are several filtering options at the top, allowing you to view data for a particular user, switch between the Watch Events and WatchLists data, and for Watch Events you can select the Source (Played or manually Toggled).
Even though there is a "Refresh" button to manually refresh (you can watch new data stream in from CMC), every time you change any of the options the report automatically refreshes.
All of the columns are sortable, and clicking a second time reverses the sort direction.
Additionally, when you select one or more records, an option to "Delete Selected Record(s)" will appear at the bottom.


Watched Event/WatchLists for Deleted User Accounts
When you delete a User Account, you are warned that you may lose their Watched Event History and WatchLists. But actually, this data is not deleted with the User Account.
Instead, all Watched Events and WatchLists for that user are preserved, but unlinked to any user account. You can still view the reports and see this data.
If you later create a new User Account, it can re-link to this data. You may or may not want this result. If you don't want to link a new User Account to old data, then you either need to delete the old data, or keep creating New User Accounts until you get to a new ID that is not associated with historical data.