Huion Tablet drawing area

Found this, it fixed my issue which sounded similar to yours.
https://forum.kde.org/viewtopic.php?f=139&t=125532

Huion are violating* a USB standard by skimping on naming their stuff, so look for the generic numbers for their tablets. This is the code for HUION New 1060 for example: HID 256c:006e Pad

xinput  # get the IDs for all relevant pieces of my tablet.   

blah blah: HID 256c:006e Pad id=17
there might/should be two devices, Pad and Pen.

xrandr  # get the names of my displays  

look for the ones showing 'connected' like HDMI-A-0 connected
and maybe DisplayPort-2 connected

Then you tell xrandr to stick the id's to the screen you want Krita or Photoshop on, such as if you were using a HDMI port to main screen:

xinput map-to-output 13 HDMI-A-0
xinput map-to-output 14 HDMI-A-0  

that was mine.
it resets after a reboot. thanks to that user timotimo!