You likely have “Display Scaling” set to high.
(There is a limit to what SketchUp supports - I think it’s either 125% or 150%.)
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Display Scaling changes for the Windows 10 Anniversary Update - Microsoft Technet Blog
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Windows scaling issues for high-DPI devices - Microsoft Support
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Use Windows 10’s individual display scaling to perfect your multi-monitor setup - PCWorld
Other searches: win10 display scaling - Google Search