Hello,
It's very simple to tally the Antivirus machines.
Ofcourse, if all these machines are managed, they would report to the SEPM, and on the right hand side of Home screen on SEPM, you would see these as below:
Make a Total of these machines with the Virus definitions and these would be the total of the Managed SEP machines with Virus definitions.
Easy!!!
Incase, if you are trying to take a Log or Report of these, then you can Export the Computer Status Report or Audit Report.
Export the computer status logs (Monitors > Logs > Computer Status) and then rename the exported file into .csv
About the information in the Computer Status reports and log
About the reports you can run
Hope these Answers your Question!!!!