I opened a new moisturising cream, and the surface was sunken. Has it been underfilled.

There is a fixed amount of space in the upper part of moisturiser containers. This enables the cream to expand and contract depending on the temperature. So if the container gets hot because of where it is stored or a change in season, and the product expands, the cream will not seep out or cause the container to break. In other words, it’s a cushion of air. When you open a new product this space may make it look underfilled, but don’t worry- the prescribed volume is there. This space, necessary to allow for volume change, is present not just in cream containers, but also in other beauty product containers too.