plywood size for kitchen granite counter base?

plywood size for kitchen granite counter base? Images

plywood size for kitchen granite counter base?

plywood size for kitchen granite counter base? Description

I will install new stand (http://maplered.com) ard sized 24" deep kitchen cabinets and (http://maplered.com) intend
to have a Granite (http://tanbrown.org) Counter (http://GialloFiorito.com) .  What is the proper size plywood for the base
so that the Granite (http://tanbrown.org) edge protrudes out over the edge of the cabinets?   
24"?   24-1/2"? 25"? or ?  Thanks