GUI 2D Bounding Box

I saw this GUI bounding box while I am looking at the HOTween’s documentation page.

I know how to control the Texture2D position and size using script but I cannot figure out how can I access the 2D box data from a 3D object. Furthermore, the bounding box in the right are reacting to multiple objects.

This is the page I saw the GUI bound box.

I will be very glad if someone can point me at the right direction.

One method is to use Renderer.bounds. Take the corners of the enclosing space for each object and translate them to Viewport coordinates. Then figure out the minimum and maximum values.