Hello!
It is impossible to implement what you want through the settings, but it can be done using program code.
But - I strongly advise you not to do this, this is the wrong approach to work!
The fact is that the document list form is a dynamic list, and if you add code to the program that will receive the totals for documents, then this code will be called every time the user does something with this list: scroll, set filters, etc.
This will negatively affect the performance of the program interface. Simply put - the interface will immediately start to "slow down".
Therefore, if you need to see the totals for some documents, then the system has reports for this.