You give 'points' values in the combat ratings. How many ships is each one worth?
Each ship class has a 'strength' rating assigned to it. Each time you destroy a ship, it's strength rating is multiplyed by some coefficient known only to Matt and added to your combat rating. Obviously, more powerful ships yield a higher strength rating, but if you want to find out the exact strength of a ship, EVula's Survival Guide has the strength of each ship listed in the 'shipyard' section.