In recent years, the trend of cheating customers by unscrupulous Chinese sellers is gaining momentum with enormous speed.
With H2testw, you can write and read how much data the storage device is actually capable of holding. This can work with network drives, hard drives, SD cards and USB sticks. https://www.softpedia.com/get/System/System-Miscellaneous/H2testw.shtml
You'll need Administrator rights to run it, but thanks to this the process of testing is so fast that you'll be provided with the real information about your media health and speed in about 5 minutes. You can measure speed of your media and you can recover it in one click if it's fake. https://flashtest.alexkhoroshev.ru/?lang=en