There is no 500GB capacity inside the flash. It is a vendor programmable controller and it is actually some low capacity which loops its actual size repeatedly to emulate sectors that do not exist. Assuming it is 8GB stick, writing beyond this location will actually begin writing at the start of the 8GB effectively overwriting the information.
for 500GB flash drive it would need at least 4 NAND chips.
Im curious, what controller is on the flash drive? I cant make it out in the image.