We don't know how does Magic Earth's routing work (might be a good thing to ask them), but typically it would try to use roads that will get you the closest to the address.

So the idea would be to move the address point that is inside the building closer to the edge that faces the correct parking lot. 

Other things that could possibly help is having the main entrance node and the parking lot area mapped. And perhaps adding a footpath from the parking lot to the entrance.