Why did my MacBook Pro osMojave 10.14.6 emit the startup chord twice when I turned it on?

My MacBook Pro osMojave 10.14.6 began the startup, but, immediately displayed the power cord indicating it needed to be connected to power. I plugged it in, got the red charging light on the magnetic connector, and turned it on.

The startup chord sounded twice in succession, and when the login display appeared, it looked smaller... like it had shrunk a little bit, but, I’m not certain. Was the startup chord sounding twice significant? And, why might my login screen appear to have shrunk slightly?