Created C-image.DIM file is a text file containing image parameters. Since files on FAT volumes are limited to 2GB, the image file will be automatically split into 2GB data chunks (files). Image Data chunks would be: C-image.000, C-image.001, C-image.002, etc.
If not enough space exists on a target drive, you will be prompted for another location where you want to store remaining chunks (files).