Unfortunately, tags on the reader are stored in a separate XML file, so there is no simple way to transfer them back to calibre. And no, there isn't anyway to transfer from reader to calibre directly. It's still a simple process, just select all books, click save to disk and then use the recursive import feature of calibre.
EDIT: And as bob pointed out, if you have a 505, you can just use recursive import directly on the folder containing the books in your reader
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