Strength per X relates the Thresholds below. Every credit spent on bounty for any player plus the number of planets and trade ships get added together. If it passes a threshold, the threat level increases.
Warning times are how often the raids launch.
Send Raid Time is how long you have to bid before they launch.
Strength Threshold determines how many ships are in the raid. That in turn is determined elsewhere in the gameplay.constants file. It's a number of fleet supply, though the actual ships are random.
In the pirate window, you'll see the Threshold it's at. (Severe, etc.)
