System Preferences - Displays - underscan

Configuration - new Mac mini 2018 running up-to-date Catalina with HDMI connection to Hitachi HDTV for a display.

In System Preferences - Displays, I set the underscan to the first hash mark in order to pull the top menu bar down slightly. When I power back up the next time, the display is not underscanned. When I return to System Preferences - Displays, the setting is still there. When I adjust it to off, the display does not change. When I adjust it back to the first hash mark, the display underscans as expected.

Any advice about how to make the setting persist?