This kit contains special code modifications extending the maximum score from 99,990 to 9,999,990. Original asteroids when it rolled over to zero would reset the difficulty. Around 30,000 and 35,000 points asteroids would become more difficult including no more big saucers. The extended scoring feature of the asteroids kit does not reset the difficulty when it reaches 100,000 and it continues to stay difficult.
Below are some screen shots produced with MAME showing the extended scoring.
High score table beyond the original limit of 99,990
99,160 and about to roll to 100,000 points.
100,220 points and still going!