Don’t trust the operating system on flash drive capacity

Did some idiot tell you your lovely new flash drive is a fake but you know it isn’t because the operating system tells you it is exactly the advertised size? Not only that but you put some files on it and it works?
You just bought a shiny new 16GB flash drive on Ebay or elsewhere on the Internet, waited with anticipation for it to arrive – and when you stuck it in the computer and looked at the properties this is what you saw:

The only thing the properties box shows is what the operating system “thinks” the size is. This is not the same thing as showing the TRUE capacity of a drive!