The very best program for determining whether or not your SD card or USB drive has been hacked, and what its original size was, is the brilliant German utility called h2testw.exe, the results from which are accepted by Paypal as evidence that the device has been hacked and is counterfeit. A google search will find it for you very quickly.

I bought a couple of purported 64Gb drives from AliExpress recently and at only US$8 I had a pretty fair idea they'd be fakes, and sure enough, they were. I simply sent screen dumps of the results of h2testw.exe to the seller and he didn't even try to argue the point. He immediately refunded my money under AliExpress's Buyer Protection Program.

When he told me that he wanted the drives back, I told him that he wasn't getting them because under AU law it was illegal to send counterfeit items through the mail. That was the last I heard from him (and I even made almost a dollar on the reverse exchange rate as the AU dollar had fallen since I initially bought them. 🙂