How to set the Committed time based on Area and subarea?

Hi Gurus,

I have couple of questions in Service level management (SLM)

I have created one entitlements (Service) under agreements. I can see the priority field under metrics where I can define the response time and resolution time based on the Priority field.  I want to set the response time and resolution time based on the Area and sub area field in service cloud. How can we do that?

What is the use Service Metrics record when I create under Administration - Service?

Thanks,

MOhan