USB/MP3 Player is not displaying the actual capacity.
It is surely a problem of system files on the USB drive.
Above all, read the user guide of the device and verify that there is no utility provided with the key to reset or reformat it. If such a utility is present, please use it before applying the procedure below.
Otherwise, to reformat and repair the USB key, it is possible to use standard Windows tools. Insert the device into the USB port of the PC, then go to:
Select the appropriate drive (USB key) in ensuring that it is not a hard drive system!
After making sure to backup the key data on the disk, delete the existing partitions on the key (right click / delete the partition). Then format the key to FAT16 using all available space (right-click/Format). If the key has a capacity of over 2GB use FAT32 format.
If space is displayed is below the capacity of the device, it is probably a hardware problem, in which case it may be necessary to contact after-sales service.
It should be noted however that a difference of about 10% can be observed, depending on how the manufacturer that recorded the bytes. To be exact, according to a manufacturer beliefs that a Megabyte equals 1 million bytes or 1024 * 1024 bytes, a key of 512 MB can display a capacity of 512,000,000 bytes or 488,481,250 bytes.