The first example is a text book sleep graph. When sleeping you go through sleep cycles that last for about 90 minutes, these cycles go from deep sleep to shallow sleep and dreaming.
If you look at the graph above you can see that the peaks are about 90 minutes apart – these are the sleep cycles of this person. You can also clearly see that for every cycle the person goes into less deep sleep, this is typical for a normal sleep graph.
The second example has a bit more irregular sleep. The user did probably not sleep as well as in example 1. In this example the user’s partner got up at 6am. This is clearly seen – the user was awake or nearly awake at around 6am when her or his partner got up.
This is how a graph will look like when the phone has trouble sensing your movements. If you see graphs like this make sure the placement test in sleep cycle works well. During the placement test the phone should make a sound every time you move in bed. You can also try placing the phone closer to your body.
This example is not a good nights sleep. Although alcohol can make you fall asleep easier it makes it hard to sustain a full night of good sleep. The first half of the night the person goes into some deep sleep but during the second half a lot of time is spent being awake or nearly awake.
More info is available in the FAQ