Why does Quicken use one category for most of my transaction when I download them

This problem started a month or more ago. When I download my transactions for my discover card account, the category is installed automatically and in transactions it is listed as medical:insurance. This is whether or not it actually is related to insurance. It is frustrating when this happens. It used to only happen to transactions for Walmart. Instead of inputting Groceries, it would put in the medical:insurance category. Now it does it for many many more transactions. What do I need to do to fix this. I can't find anything in the help area relating to categories.