Windows not accounting for physical dimensions of monitors

So I have 3 monitors, two 20 inch and one 40 inch that I have arranged with the smaller two side-by-side on the bottom and the biggest above. They all are 1080p, but the problem I'm having is the scaling of the largest monitor.
What I want is for Win 10 to scale the biggest one's width (and height equally) to be the width of the bottom two combined, like in reality. However, it scales all 3 to the same size and I don't know how to fix this issue.

Extend. I can change the scaling factor now (and set custom ones) but that only alters the size of the UI.
Also, thanks for posting a reply! I've been trying forums for a while now with no responses.

yeah, the UI or GUI scaling isn't the problem, it's windows not scaling the relative size so that the bottom edge of the top monitor spans the top edges of the bottom two side by side so that I can move my cursor from any point of the bottom two upwards and it'll enter the top one.

Yes, that last image is how I have them arranged, but the biggest and topmost is a 40 inch while the bottom two are 20 inch. in actuality, the top one is the width as the bottom two side by side. But it sets them all as the same size.

I see, mine are all the same resolution (1080p)

Windows doesn't care what size the monitor is, all it sees is the resolution and works with that. For what you want you are going to need something like this,

Free vs Pro Binary Fortress Software


which from looking at the comparison list, the fre version should be able to do what you want.