Thanks for sharing a screenshot of your shipping settings. Since these are weight-based rates, the rate your customers are charged will be on the total weight of all products in their cart, as well as the weight of your default package in Settings > Shipping.
I recommend double-checking your product weights for the products you're adding to your cart. You can do this in your Shopify admin by heading to Products and selecting a product. You'll then be able to review your product details, including the weight. If you can share a screenshot of the product in your admin with the weight visible, that would help me get a better idea of why the incorrect shipping rate is being applied.
It would also help if you can share a link to those particular products on your online store, so I can test it out here on my end.
Looking forward to your update!
Julie | Social Care @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog