How many leaves fit in a leaf bag?

My kids found out that 40,000 leaves fit in one of the tall paper bags. They did this by first making three piles of 100 leaves which they counted, then making 10 piles of 100 leaves to make 1000. Then they made 9 more piles of that size to see how much 10,000 was. Then they made 3-4 of those piles and started filling a bag. They got 4 of the piles in so that's how we get 40,000. Discounting systematic errors, I would expect the standard deviation to be about 20% based on propagating the standard deviation of the initial three piles of 100. I would say the worst case is 100% error or a factor of 2.