how -

The hinge on my lunchbox is a little raised on the sides - is this normal?

It is normal for there to be a space at the back (hinge) of your PlanetBox.  In fact, it is an intentional part of the design, to allow for flexing and sealing of the dippers.  The back of the PlanetBox does not need to be flush with the hinge.  The space can be a little more or a little less than what is shown on this picture attached – the variable amount of space will not affect the functioning of the lunchbox.