Recording Application M and S Metrics
You can record metrics data either :
The number of defects detected in each of the categories for the application for the period about which data is being collected. The number of defects found in production is an indicator of the maturity of the Development Processes capability to find and remove defects.
The Defects are rated by severity. For more details on the severity ratings see : Effort Data (D&E - Projects and Releases).