Technical Note: How do I see which alerts a policy would have triggered in the past

Once you have created a Policy (via the Policy page), at the bottom of the page, FortiInsight will indicate the number of previous alerts which would have been triggered by this Policy, based on the data FortiInsight has collected to date. 

Navigate to the Threat Hunting page, where the policy details will be prefilled in the search bar, to see which events would have triggered alerts.