The bonus is when you get extra points and with that extra points you get more kao coins. Like in the quiz you do everyday you will keep on getting same coins and not different, that's why it says "rare" and "ultra rare". So for common I think = 10 points, rare= 50 and ultra rare = 100; Each coin you get has a specific point on it, and then when you collect it, it adds up, when it hits 50 or 100 or 10 you will get "BONUS". After clicking on it you will get coin from the three categories. IF you get all common coins, it will only show after 50 and if you get all rare coins it will show after 100.