Here the complete information for my system:
I am running Wolfram|One Personal on a Lenovo ThinkPad laptop workstation W530 with a 1920x1080 Display under Windows 10 Pro in Germany.
In[218]:= SystemInformation["Kernel", "ReleaseID"]
Out[218]= "12.1.0.0 (6776260, 2020031901)"
In[219]:= SystemInformation["Devices", "ScreenInformation"]
Out[219]= {{"ScreenArea" -> {{0, 1152}, {0, 648}},
"FullScreenArea" -> {{0, 1152}, {0, 648}}, "BitDepth" -> 32,
"Resolution" -> 120.}}
In[220]:= CurrentValue["ConnectedDisplays"]
Out[220]= {{"Region" -> {{0., 1152.}, {0., 648.}},
"FullRegion" -> {{0., 1152.}, {0., 648.}},
"PixelDimensions" -> {1920, 1080}, "BitDepth" -> 32,
"Resolution" -> 120., "Scale" -> 1.66667}}
In[221]:= Options[$FrontEnd, "Magnification"]
Out[221]= {Magnification -> 0.8}
The last Magnification setting is a bypass which was set by
Options Inspector->Global Preferences->Notebook Options->Display Options->Magnification->0.80
or programmatically by:
SetOptions[$FrontEnd, "Magnification" -> 0.8]