Do kitchen cabinets have to be totally leveled before granite is put on?

New kitchen cabinets are going against a wall opened to the dining room. The cabinets aren't totally flush with the top of that wall, there's only 2mm difference if that...is that going to be a huge problem for the people installing the granite? Will they make it level when they put it on or will they make me do it myself, and if so how can I fix it?