External Monitor Screen too large
Typically this is an issue when you connect over HDMI and the display / TV / monitor settings can be adjusted to turn off or reduce the “overscan” which in effect is zooming in in the center of the signal. 

Search here for overscan and you’ll see a lot of results:


How to solve Mini DisplayPort to HDMI Overscan problem? (Part of the screen is missing)
Display&#39;s native resolution not registering properly


Specific steps for HP 25bw monitors are as follows:


Press the Menu button to open the OSD settings.
Scroll to "Image Control..." and press OK.
Select "Custom Scaling" and press OK.
Select "Overscan" and press OK.
Select "Off" and press OK.
Select "Save and Return" until the OSD menu closes.


Same steps will work for MacBook Pro 2018 connecting to HP Pavilion 25xi.