The Project Request Manager template comes with several built-in metrics that give the number of requests with the different statuses. To see them, click Settings | Site contents, and then click Project Metrics.
Draft - with a Warning value of 50 and a Danger value of 100
Review - with a Warning value of 25 and a Danger value of 50
Pending Decision - with a Warning value of 50 and a Danger value of 75