Cut, from defined level or existing ground

I am new to the software and have a question. i recently set platforms and roads on a project and am not sure how to double check quantities, as i have some concern of being short on the cut.
Question- once i set the defined elevations and finished contours on the paving, does the cut quantities come from the defined levels OR do the cut quantities come from the existing ground elevations?
Can i double check quantities by using the topsoil spread tools and fill the areas?

thanks