Mac Mini 2018 HDMI underscan/overscan

I plug an HDMI monitor (Prolite E2409HDS) into a Mac Mini 2018 via HDMI. The image on screen is underscanned. The monitor itself has no underscan/overscan setting. The MacMini has no underscan/overscan setting available in the Preferences pane. Change resolution makes no difference.

How do I correct the underscan?

( I though this kind of mismatch should have gone out when analogue was replaced by digital? There's no ambiguity about how many pixels are in an 1920x1080 image. What gives? )

thanks.