title: Calculate a percentage of two values in Zabbix
body: <p>I'm reading information from a Xerox Photocopier via SNMP, i'm trying to read the status of the toners. This machine doesn't supply this information in a percentage left but thats how i would like to display it.</p>
  
  <p>For instance the current reading for the black toner is 460, there is another key for max capacity for the black toner and this is 4600. So there is 10% left of this toner.</p>
  
  <p>How or where can i enter the calculation to make this work on the SNMP item?</p>