CDC puts it at approximately 50-70 million adults.
https://www.cdc.gov/mmwr/PDF/wk/mm6008.pdf
That would be closer to 24%.
But most people report sleeping less than 7 hours, which affects a multitude of things, including your overall health. Not to mention the people who report falling asleep unintentionally.
Believe it or not, teenagers need up to 10 hours of sleep.
I have delayed sleep phase syndrome. I am at my most alert in the mid-afternoon but I can easily stay up to 2am without medication. Then I sleep for 8-9 hours which makes it tough to hold down a normal job. Thankfully I have an accommodation that allows me to start 3 hours after everyone else.
I bought one of these on a whim when the first came out, but honestly I never used it. I do hope Apple continues to support it and improve on it.