Checking time values for screen locking

I have chosen a time value (in the system configuration utility “screen saver”) after which the screen can be usually locked.
Now I get the impression that the screen gets locked (in a desktop session “XFCE 4.14” for example) before the selected time duration. :
I would appreciate your advices to check and adjust this aspect.

  • I am using the display manager “LightDM”.
  • I prefer to work with my software development system primarily based on the desktop environment “XFCE 4.14” for a while.