Start over on the D drive, reformat it. Then add the New and stored folder. The new folder should be about 3400GB .
You have other files on the D drive.
If you are using a complete disk for large video file storage (BVR) continuous recording, I recommend formatting the disk, with a windows cluster size of 1024K (1 Megabyte). This is a increase from the 4K default. This will reduce the physical number of disk write, decrease the disk fragmentation, speed up access.