When they first came to do the estimation, they said they don't know how much they will dig. Turned out they dig until they feel the soil is packed enough to hold the weight. It was over a ft deep of soil that removed, replaced with Gravel, limestone. Packed down many times layer after layer and finished with very nice and flat patio stone. They ensure the grading is well measured and ensure no water will flow toward the house or stay still. For the flower bed, they took extra time to make sure it is a perfect circle and all round corner are uniform. Been a year now and it still very solid, stone are tightly packed, no cut corner at all.