Are you sure that it is 256Gig? I would bet that you have a fake USB flash drive. Fake flash drives that are smaller than their stated capacity are very common, coming mainly from China to catch out the unwary. I test USB flash drives by filling them up with large ZIP or RAR files and using the program to test the integrity of the files. If it fails you know you have a fake flash drive and should return it to where you bought it.
You are aware that FAT32 has a 4Gig file size limit?
Yes I am aware of the 4gig file size limit, all my films are around 2 to 3 gig, on my computer, it says 242gb free space left after the 3 films that I already have on there