Apparently, the scammer took two 512MB Flash drives and then add hacked firmware that makes it misreport its size. This means that when you write a big file, hacked firmware simply writes all new data on top of old data, while keeping directory (with false info) intact.
We have seen a few of these in fact we suspect one unbranded one crossed our desk a few months ago. That one was seen on Facebook. While we could not find anything viral on board it did manage to trigger the Windows 11 install on our rather unconventional PC. When we looked under the bonnet rather than the 10 TB promised there was a 100 MB thumb drive wired to a USB. The computer insisted that it was 10 TB.
The hardware structure between the two scams is similar. On the inside, this "SSD" looks like two small-capacity microSD cards hot glued to a USB 2.0-capable board. This board's firmware has been modified so that each of these cards reports its capacity as "15.0TB" to the operating system, for a total of 30TB, even though the actual capacity of the cards is much lower.... It preserves the directory structure of whatever you're copying, but when it's "copying" your data, it just keeps writing and rewriting over the tiny microSD cards.
Until the big retailers and advertisers crack down on this particular scam it is probably better to buy only branded SSDs from reliable retailers.