On a supply-demand curve affected by price ceiling (in the case of a deficit) or price floor (in the case of a surplus), both would be the gap between the demand for a product and the amount supplied of said product in the market.
A deficit is the gap when the amount demanded is much greater than the amount supplied (since the ceiling, being below the equilibrium price, is at a point where the amount supplied is low because suppliers don't feel the desire to produce at such a low price, but demand is so high because people love a good deal).
A surplus is the gap when the amount supplied is much greater than the amount demanded, where the price floor is above the equilibrium price, and supply is high because suppliers are producing at high-production since they are selling for a good price, but at the same time, demand is low because consumers don't want to spend that much on the product.
Hope that helped! =)
