I've started using grids for more responsive designs, but in several places, I can't make the cells as vertically short as I want. Fx, the big gray area at the bottom in the pic - how do I remove that? I've tried adjusting the height in the grid editor on the right, but nothing helps. This is very frustrating.

I've started using grids for more responsive designs, but in several places, I can't make the cells as vertically short as I want. Fx, the big gray area at the bottom in the pic - how do I remove that? I've tried adjusting the height in the grid editor on the right, but nothing helps. This is very frustrating.