I have a selection of products. Most of which are in more than 2 categories.

When I go to the Cart admin for a product I can see it has a Category Name. If I then click on the Categories Tab, I see all the categories checked that the product is in.

The Category Name that is displayed bears no relation to the categories list it is in. For example, if the product says, category Shoes, and blue shoes, and lace ups are also categories that are checked.

What makes it decide that blue shoes is the category that is shown in the summary? Why won't it sho the topmost category, or indeed all of them?