Based on the answers provided, here are the corrections needed for the 3D object:

1. Modify the object to resemble an upside-down table. This means it should have a flat, broad surface that represents the tabletop in an upside-down orientation. Ensure that this modification does not affect the "U" shape of the object.

2. Adjust the dimensions of the upright columns to make them wider than the horizontal sections. This change should not affect the object's extrusion in one dimension or its "U" shape.