If the soup is too runny, prepare a slurry of cornstarch, arrowroot powder or any flour and water in a small bowl. Add this to the soup. Then cook the soup on simmer or in saute mode till it thickens. 1-2 tbsp of cornstarch for every cup of liquid is ideal. Alternatively, you can also add a boiled mashed potato or finely chopped carrot to thicken it. If the soup is very thick, dilute it with some water or stock. The consistency of the soup is a personal preference. I like my tomato soup to be thick and creamy.