Offsetting arc makes it a curve?

[njsanna]

I have a shape that is extruded 4" for a stone top cap. I want the top cap to have a 1" overhang over the pillar below. To make the pillar I offset the top cap 1" and extrude down. When I go to apply textures the textures show as if there are multiple faces.
The Entity Info for the offset arc shows it as a curve now.

Why?
How do I solve this?

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[Box]

I can't see an Arc or a Curve in your screenshot.
Attach the model so we can see what you have.

[slbaumgartner]

Maybe it's an optical illusion, but the front surface of the box looks slightly concave to me. As @box wrote, we would need to see the model to say more surely.