The problem is relevant to the disk "allocation unit size".
When storing files on a disk, they are not stored based on the actual size of the files, but based on the "allocation unit size".
Thus, when the "same file" is stored on a disk with a “different allocation unit size", the occupied "disk space" could differ.
Take the following picture as an example, the disk "allocation unit size” is 1024KB"
Multiple files with the actual file size of 4KB are stored in the drive. Each 4KB file occupies a disk space of "allocation unit size = 1024KB" for storage.
The actual file size and the occupied disk space will have a 256 times difference (1024/4=256), as shown in the figure below.
Before saving the files, please refer to the source file, set an appropriate "allocation unit size" and then format it.
Note: Formatting will delete all files inside the disk.
Please back up the files before proceeding with the formatting process.