"Points" are based on the damage you do to the enemy planes. All damage you did to enemy planes, whether you got the kill or not. Its not directly related to the number of kills you got.
If you line up on a bomber and get solid continious hits on it, but only get credit for an assist, you may (likely even), get more points than you would for a snap shot that removed a wing from a fighter that you got kill credit for. Why? Bombers generally absorb more damage than fighters before fatal damage occurs. Same could be said for shooting a fuselage in half vs shooting off a wing. Different areas of the plane absorb different amouts of damage before they fail.
Fankly I wouldn't worry about that stat. Worry about performing well in the other 80% of stats that make up the total fighter score. The points vs enemy is the only fighter stat accumulates, and the only stat that rewards quantity over quality...but its only 20% of the score. The other stats are the ones that reward your personal average performance.