Well, it's a survey; the vast majority of the time I wake up 'unaided' between 06:40-07:20 (I have my alarm clock set to 7:30 as a fail-safe), but if you'd ask me what time I wake up, I'd say "around 7am", which then would be recorded as a precise value.
I was more impacted by the fact that every hour, on the hour, there's a pretty significant shift. Of course, 5pm is the big explosion, but pretty much we live our lives based on the clock.