Hello, @Bharani Eswaran !
It looks like you tagged this with Azure Lab Services (an Azure managed service that allows you to create classroom labs) so I'd like to point out that Azure Lab Services is charged by Lab Unit and is not part of the free units/500 minutes free a month for Automation job run time:
https://azure.microsoft.com/en-us/pricing/details/automation/
For the free units/500 minutes, it is important to note that these are not available to subscribers using rate plans providing a flat discount or a fixed monthly credit amount. Does that sound like it might apply to your subscription?