Hi Ricky,
I assume you are are extending the display rather than duplicating
when duplicating, the settings apply to both monitors.
When extending the desktop, although custom scaling and text size applies to both monitors, the drop down box in Settings -> System - > Display -> scale, only applies the selected monitor.
As this "scale" dropdown will only allow a setting of greater or equal to 100%
you would need to adjust the laptop monitor.
go to settings -> system -> Display
make sure that the laptop monitor is selected in the graphic at the top of the page
then under "scale & layout" click on the dropdown box next to "Scale" (avoid the chevron on the far right)
I suggest you make small adjustments until you find one that works for you, try 125% to start