What can I do if there is leftover product I cannot use?

We have investigated and found that this is an optical illusion caused by the unusual packaging. Just to explain further, the cleanser is contained in a plastic bag inside the outer bottle. As the product is used the bag gradually collapses due to air pressure until the sides of the bag are in contact with each other and there is nothing left to pump out. At this point the bag is virtually completely empty. However, the inside of the plastic bag is still coated with a thin layer of product and so, when looking through the bottle, it can look as if there is product left.