Viewport Size vs Layout Size

Newbie question: When I create a new project I select the preset 1080p landscape and that sets the viewport to 1920 x 1080. Perfect.

But, when I look in that project at the default layout size it says 3840 x 2160.

What's happening?

The layout size is basically how big the level is. It's the editing area in the Layout View and the default scrollable area.

Construct defaults the layout size to twice the viewport size, because if the layout size is the same size as the viewport size, then by default you can't scroll anywhere. That resulted in a lot of beginners asking "why doesn't my game scroll", so the default is to provide a scrollable area.

That makes a lot of sense. Thanks for the help!