When reading a graduated cylinder, a proper way to do it is to read at the level of the lower or upper meniscus. It is the curve formed at the upper part of a particular liquid that is close the surface of its container. This is caused by the surface tension. It can be in a concave or convex form depending on the characteristics of the liquid. It is important especially in performing laboratory experiments as it indicates the true level of the liquid in the container. When reading from apparatus, the lower meniscus or the upper meniscus is taken as the correct reading otherwise you would record a wrong data.
