This is the current combined zoom factor that combines all the following:

• Browser zoom percentage setting.
• Operating system DPI scaling setting.
• Operating system accessibility scaling setting.

Your TestUFO is in an ideal configuration when you see a green 100% combined zoom factor needed for 1:1 pixel mapping.
It is also possible to combine zoom factors if they result in clean numbers (e.g. 200% DPI combined with 50% browser zoom).

Please note, certain additional scaling behaviors are not detectable:

• Non-Default resolutions in MacOS. Please select Displays -> Default resolution.
• Pinch-Zoom setting on a touchscreen. Please undo any pinch-zoom in your browser.