Sorting the Grid

I examined the bowl of green and red apples sitting in chaos. Disorderly! Three green, four red, tumbling together with zero organization. Unacceptable! I immediately set to work. I hauled the fruit out onto the clean white grout grid of the counter. One green apple aligned at coordinate zero. Tap! I pressed my ruler against its flank to keep it steady. Then a red apple beside it, spaced at an exact gap of three centimeters. One rolled backward. No compromises! I blocked its retreat with a sharp flick of my ruler edge. Now they form an alternating, disciplined column. Seven units accounted for. Perfect sequence!