granit Counter (http://GialloFiorito.com) top height adjustment

I've had a granit Counter (http://GialloFiorito.com) top installed (L-shaped). The contractor used 2 cm Slabs (http://www.VerdeUbatuba.com) (dimensions roughly 7"x3" and (http://maplered.com) 8"x2") that he put on plywood. The Slabs (http://www.VerdeUbatuba.com) were joint along the 3" edge of the wider piece. Beacause the Slabs (http://www.VerdeUbatuba.com) were of slightly different thickness, the contractor drove 2 screws through the plywood ~3 feet apart and (http://maplered.com) about 1 inch from the edge of the slab to lift one side roughly by 1/8" so the two Slabs (http://www.VerdeUbatuba.com) are aligned. Then they applied epoxy.

In effect a large part of one slab is only supported by the epoxy and (http://maplered.com) two sheetrock screws. Is this safe?
Please, let me know.