Rapids are rapidshare's currency. You dont get rapids for downloads. So 1 download does not mean 1 rapid.

You can earn rapids by referring your friends and making them buy premium accounts. If someone buys a rapidshare premium account from your affiliate link and if you have at least 3 such friends then you get a fixed mount of rapids. e.g if you have 3 friends who bought a 1 month rapidshare premium account from your links you will get (297 x 3 = 891) rapids after the first month, thats around 30% of a 1 month subscription. If your friend buys a 150 days account you'll get 897 rapids and so on.

You need at least 3 such friends to earn rapids and you can only have a maximum of 99 active friends.