Considering the current situation with the price of Bitcoin and income from advertising network reward is good although each user's would like that time between claims is a little less then 540 minutes.
There is no % for reward you offer,so it wold be good to add what are the chances for each of the possible winnings.Another thing that I do not like concerning the other captcha,when typing letters / numbers they are not show in box.This is probably for security reason,but I'm not sure that helps significantly.
Well, I have removed the % for some reasons. And, I didn't noticed the color problem, I don't why it was yellow! Now, you can check, the color is black. And also, "probably for security reason", no, a color can not improve the security.