Discuss this with the surveyor. He likely set his primary control using GPS. Most of the time (but not always) GPS units will report grid coordinates. If you scale the coordinates up to surface, you are best to use a point that is fixed on the ground (ie. primary survey control point) and close to the center of the project, so the grid and surface coordinates are the same for that point. With a small site, the surveyor can stakeout the project using either grid or ground coordinates and be OK, assuming it is typical development stuff, ie roads, sewers, drainage, etc. If you scale based on 0,0, you will shift the entire site a significant amount...usually 2 or 3 feet. This can cause havoc when re-establishing survey control and staking out the project.