1. Some of them sleep 8 hours, others 5 hours.
2. Some get up at 7am, others at 5am.
Also, that clock visualization is stupid. Since there are 24 hours a day it makes absolutely no sense at all.
And that clock visualization, especially with the hands included, is such a poor way to deliver information. After several minutes of parsing them, I finally think I deciphered what they meant.
Especially when the first clock is using hands at 8 to mean 8 hours, and the second is using hands at 8 to mean 8pm, and the third is using hands at 8 to mean 8 am.