Greetings, steevo987.
Welcome to the Apple Support Communities. We can understand why you’d want to know more about the Screen Saver warning you saw.
“A warning symbol indicates if your display is set to turn off (as specified in Energy Saver preferences or Battery preferences) before the screen saver starts.” Change Screen Saver preferences on Mac
That being said, since the screen saver time frame is under the threshold for your screen being turned off, we'd like to look into this a bit deeper. To get started, if you change the Energy Saver settings to turn the display off after one hour, does the same behavior occur?
If you change the screen saver, does the same thing occur as well? Alternatively, if you test this behavior in another admin user, does it appear to be resolved? If you've never created another admin user for testing, check out: Set up users, guests, and groups on Mac - Apple Support
We hope this helps! Thanks for being a part of the community.
Sincerely.