Well it probably is correct depending on the style but you will still need to import them again.
Problem is it writes a file name with a timestamp in the name that is written to the database.
You can try gizmo's suggestion but I think it will not work because you deleted everything.
I also found that you had a similar problem two years ago.
So I would suggest to delete a style and then import it again.
using:
Control Panel ยป Styles
import style
If you don't delete one first you will need to rename the style with a different name
Then you will also need to assign a default style when done.
Try one style and see how it goes.
