Understand Policy Delivery Control (FortiMail)

Can someone provide a more detailed insight into how Policy, Delivery Control works? The information in the Admin Guide as well as the CLI Guide is limited. I am considering implementing this feature but would like to better understand how it works and what impacts I can expect...how long will email messages be delayed for example...is this feature configurable, etc.

An example is attached of my starting point for Gmail.

Currently running FortiMail 400E Appliances running 6.0.3.

Thanks