I usually fall asleep very quickly, especially if I'm listening to a podcast. I set the timer for 15 minutes, but often I'm asleep in five minutes. And then sometimes I wake up a few minutes after the podcast has ended before falling back asleep.
I fell asleep quickly like usual, but I didn't wake up for a while. I figured it was middle of the night until I looked at the clock. I was expecting it to be 3 or 4 in the morning. It was 11:22. I'd been asleep for less than an hour before waking up.