Times more energy than
a magnitude 4.0 earthquake releases just over_
a 2.0 magnitude earthquake.

The magnitude scale is logarithmic. That just means that if you add 1 to an earthquake's magnitude, you multiply the shaking by 10. For example, if the magnitude of one quake is 6 and another is 4, than the difference in magnitudes is 2, so the stronger earthquake shakes 10^2 or 100 times as hard as the milder one