The controller is where this whole fake actually gets pulled of. Just slapping those two chips together does not create a USB memory stick. Besides the other parts needed, the controller has a firmware flashed on to it that tells it what the exact chip is that it has available as storage. So now those fakers just take a small stick, say 2 GB and flash on to its controller that it actually has a capacity of 32 GB. Windows reports only back what the controller tells it, since it can’t know exactly how much data there really is available for usage.
Your only chance is to flash it again. For that you need to read the controller chip, the square little one, and search for the tool that is needed to flash it. Usually the first two lines indicate the maker and the model. Enter it in Google and you should find tools ready available online. You have to make sure that it is exactly the right tool for your needs. If the tool is for the chip 1901 and you have 1903 model, it most likely won’t work. Also many are in Chinese which makes it extra hard. In many cases you can rejuvenate your drive to the correct size with that.