The NP ratio tells you how many Neopoints you'll earn for every point you score while playing a game.
For example, if the NP ratio is 100 NP for every 150 game points scored, to earn the maximum 1,000 NP reward for playing, you'd have to score 1,500 points during the game.
On the other hand, if a game's NP ratio is 25 NP for every point scored, you'd only have to earn 40 points in the game to get the full 1,000 NP for playing.
Destruct-O-Match III:
Mass hysteria broke out among the citizens of Tyrannia today, as they awoke to discover their most beloved landmarks blocked by huge piles of mysterious boulders! Hungry Neopians were turned away empty-handed from the Giant Omelette, and music lovers were disappointed to find the Concert Hall completely clogged with stones. Where the boulders came from is unknown, but Tyrannia's Council of Elders is begging fellow Neopians to come to Tyrannia and smash them!