Shipping adjustments – Mercari: Buying & Selling App Review

I sell a lot of things on mercari and will continue to do so however I do have a major problem with it. When a package is shipped out sometimes when the money goes through they’ll tell me there had to be a “shipping adjustment” made and some of the money I made from the transaction was taken for that. What frustrates me is that there’s no way two small teddy bears weight 2Ibs it seems very made up for more profit. Also most of the time the buyer has already paid 5$ for shipping and 2 pound shipping is 7$ so why was I charged 8$?? It makes zero sense. If this is going to happen then don’t make shipping cost adjustable have a fixed cost for products.
Review by GgboL on Mercari: Buying & Selling App.