And if there's a lot of shaved ice, it means you can shape it back into "round" after putting the syrup on top has caused melting. They also pack that stuff in really tightly--one place they hand-patted the stuff down while I watched, and that also seemed to help. There was also layering happening at times, where they put some at the bottom, added some shaved ice to fill the bowl about half-way, then added more shaved ice, then put it on at the top.
Mind you, the places that did they layering were the expensive places. I can and have paid over 700 yen for shaved ice, and it was worth it. One place had mango shaved ice that actually had chunks on mango on the top, and I was in heaven.