The site simply provide the 5 min historical price of bitcoin since April of 2013. The predictions are solely based on how they've increased/decreased in the past. For example, on the chart if it says 65% on Tuesday at 0:00, that means every Tuesday since April 2013, bitcoin price has increased 65% of the time from 0:00-0:04 on that Tuesday. By no means is it a guaranteed trading strategy, but it provides chance of increase/decrease solely on historical price.