Why is the Least Weighable Amount Useful?

When making up an amount of preparation, the formula will ask for a specific amount of a substance. You need to know whether you can measure the amount specified on the available instruments within the stated error range. It may be that the amount is too small to be weighed accurately and you would need to prepare more than is specified.

The Least Weighable Amount indicates whether you can measure out a specified amount within the defined error range.