Film counter shows incorrect number of shots

The film exposure counter will reset if the back of the camera is opened whilst film is loaded.
For example, if someone opens the back cover after 6 shots have been taken, the counter will then show a full 10 left when in fact there are only 4. This normally happens when someone you know is interested in the product and opens the back cover by mistake, best to let them know straight away if they show interest to save your film!