Here's why:

* Meniscus: The meniscus is the curved upper surface of a liquid in a tube. This curve is caused by surface tension.

* Concave Meniscus: Water has a concave meniscus, meaning it curves downwards in the center.

* Accurate Measurement: Reading the volume at the bottom of the meniscus ensures you're measuring the actual volume of the water, not the volume of the air above it.

Let me know if you have any other questions!