There's not a single extra atom water molecule above the 2 inch mark and not a single water molecule below the 2 inch mark. It's essentially 0, right? It might not be obvious to you because you probably heard, oh, we had 2 inches of rain last night. But think about the exactly 2 inches, right? Normally if it's like 2.01, people will say that's 2. But we're saying, no, this does not count. It can't be 2 inches.