Playing with Pirate raid settings in GamePlay.constants and I see the following:

spawnShips
                minFleetPoints 20
                maxFleetPoints 25
                requiredShipCount 0
                randomShipCount 5
                randomShip
                    type "FrigateTechLight"
                    weight 2
                randomShip
                    type "FrigateTechLongRange"
                    weight 6
                randomShip
                    type "FrigateTechHeavy"
                    weight 8
                randomShip
                    type "FrigateTechAntiFighter"
                    weight 3
                randomShip
                    type "FrigateTechSiege"
                    weight 3

Two questions:

1. What is the proper format/use of requiredShipCount > 0?  I cannot find any examples where requiredShipCount > 0.
2. How does the 'weight' affect the random spawns?  What is the calculation?