Employees with the job status of active, joining and former use a license, whereas employees who are archived do not use a license.  

To see which employees are active on your system, create a Data Export for the employee's dataset. Make sure you check the include inactive users in export.  This will download a CSV of all employee information.  The checkbox determines if joining and former employees are included in the export.  Archived users never are.

An alternative approach, for smaller organizations who have enabled the Employee Directory in Appogee Leave is to count the users listed in the Directory.  You will need to sum those in Joining, Active and Former states since all 3 states consume a license.