If you are testing your shipping methods on your online store, more than likely you've had a lot of repetitive activity. This activity is stored in your browser's cache. Your browser cache is a place on your hard drive where the browser keeps things that it might be able to use again in the future. Retrieving information from your hard drive is faster than retrieving it from the internet.
During repetitive testing, the shipping address and cart content is stored in the browser's cache. If your browser thinks it sees the same shipping address and cart contents it saw previously, it will retrieve the previous rate estimates from its cache. As a result the rates you see in the checkout process won't reflect recent changes made to the app settings or the product shipping parameters.
The solution is to clear your browser's cache. How to do so varies by browser and changes from time-to-time when updates to browsers are released. To find out how to clear your browser's cache, Google it.