The items with a broken icon are the wii, ps3, xbox360, DS and PSP, it generally is ten software and five hardware sales predictions.
Winnings are determined by your prediction accuracy. Prediction accuracy for a each prediction is calculated as the difference between your prediction and actual figure / actual figure. The prediction accuracy for each prediction is divided by the average accuracy across all users for that prediction and then this ratio is multiplied by your bet on that prediction
If you want to copy & paste the "how to play" page, that might help some people, too...