When you offset a surface either with a draft or by expansion, you can specify the offset method as Normal to Surface or Translate. These options are available on the Options tab. Choosing Normal to Surface creates an offset surface that is normal to the reference surface. Choosing Translate creates an offset surface in that specific direction while retaining the size and shape of the reference surface.

The next figure shows an offset surface with Normal to Surface selected:

The next figure shows an offset surface with Translate selected: