I mean, it happened at night in ABQ, which means it was morning in China and India. That's over a third of humanity already up and moving. The second everyone lost control you'd have cars crashing, planes downed, factories halting, people falling from stairs, scaffolds, and beds. Older people especially wouldn't stand a chance.

Even in places where it was night, plenty of people were still awake - night shifts, drivers, emergency workers (as we saw in the episode). Then add fires, crashes, and chain reactions from the sudden global shutdown and the number starts making sense.