I concur too, that card is most likely fake. They're programmed to read at whatever the card wants to be marked as. And you can copy all the files you want onto it, but when you go to access them or other, they're either corrupt or just disappear.
To be sure of what size SD card that you have, use H2TestW to read and write to the whole card. It'll report back on what the ACTUAL memory size of the card is, if there were any errors, defects or other to it.
I had bought two Samsung Pro 64GB micro SD cards just this month on eBay (I know...) and I was able to copy over 20GB of files onto them. But when I put it in my G3, over 3/4 of the files kept saying they were corrupted or would just be empty folders. Looked around online, found H2TestW, ran the tests on both cards and they both came back as being only 7GB cards with numerous errors and defects. I was only getting 1.5MBps write speeds. Bootleg cards.
I bought Samsung Pro EVO 64GB from Amazon, ran same tests, actual 64GB cards with not a single error or defect.