Fake parts are extremely common when buying USB or other flash drives; it's apparently trivial to get a flash drive to report quadruple its true capacity. I wind up checking EVERY flash drive I buy for capacity; the name brands pass and maybe 75% of the Chinese brands pass.
Nevertheless, if you aren't extremely careful, there are knockoffs that look convincingly real, until you run a capacity test.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
You also need to run a performance test on flash drives, e.g. CrystalDiskMark. There are SSD drives which have the advertised capacity, but use a low performance SD card inside, instead of what should be there. That applies to both external USB and internal 2.5-inch SATA SSDs.