Are you controlling the position of the monitor from Aximmetry? If you are, that means that the both the scale and position of it is now controlled from inside Aximmetry, so you simply need to set the size of the screen to a 16:9 aspect ratio inside Aximmetry. Alternatively, you can set bake the scale onto the mesh inside Unreal using the Editor Mesh plug-in. 

You don’t set a specific resolution, you set an aspect ratio in the Scale parameter. By default it shows a uniform scale value,  but the arrow to the right of the value lets you change it to XYZ scale in the Switch Transformation module.

Hi. Thank you for your reply.

I changed the PositionScale to XYZ and now it is 16:9, but I cannot change the size. Do you know how I can do this?

Also, what is the cause of the square when reflected from Unreal to Aximmetry like this?

I would appreciate your reply, thanks.

There’s no such thing as PositionScale. It’s just scale, which is the same thing as size. If you want to change the size, you just need to change the scale parameters while keeping them at a 16:9 aspect ration in relation to each other. Like I described, it’s easier to just bake the aspect ratio into the mesh instead, so you can just change the global scale value.

Not sure what you mean with the “square reflected from Unreal to Aximmetry”? Nothing is ever reflected into Aximmetry, since Unreal renders everything.