When you hit the green flag, a large number will appear that is an exponent. It will ask you what the first exponent number is, then the second one. You must answer both of them so that when Scratch does the exponent, it gets the number on the left. If you do it correctly, then it will make a cheer sound and give you a point. The amount of points you have is in the top left of the screen, just after hardness. You can change the hardness of the numbers it gives you by moving the hardness slider in the top left of the screen. You will never win, just keep getting more points. If you answer the question wrong, then it will not give you any points. It might not be a good idea to put the hardness slider near maximum, because the last few digits will not show on the number. The last few digits can help with modular exponents, so it will be much harder.
Update: When you get ten points Scratch will try to calculate the biggest number ever calculated in it, and then stop everything. However, Scratch will never stop everything because the number takes around 7625597484987 calculations to complete! Also, the number will be way more than Scratch's limit, so it will just say infinity.