Hitting flying saucer in Frame 3 determines the point value of the rest of the Monsters of that flame.
TIPS AND TRICKS
* In Frame 3, if you hit the first 10 monsters in succession, a flying saucer appears. Shoot the saucer. Whatever number appears when you hit it will be the point value of the rest of the monsters in the frame.
* In Frame 4, be sure you shoot the first monster that appears. An accurate shot will allow you to proceed to Frame 5 & 6. If you miss the first monster but hit the second you can only proceed to Frame 5.
SOURCES Machine's picture. Arcade TV Game List Kokunai - Kaigai Hen (1971 - 2005) at page 41.