what depth in cm can a 6sqm area be covered by 0.6sqm of material

This is a volume problem:  volume  =  area of base x height  

                  which is also:  volume  =  area of base x depth

(However, the 0.6 sqm of material must actually be 0.6 cubic meters of material.)

volume = 0.6 cubic meters          area of base = 6.0 square meters         depth = unknown

----->     0.6  =  6.0 x depth

Dividing by 6.0:     ----->     0.6 / 6.0  =  depth     ----->     0.1 meters  =  depth