Remember... the Desktop is syncing books in kepub format, so even if you had the book already via ADE on the Touch, Desktop will resync in the kepub format (and, if not already done will re-download that from Kobo).
Now, what I have never paid attention to is how the Desktop to Touch sync happens; I mean I'm not sure if it uses the data already on the PC (and within Desktop) or if it redownloads from Kobo to go to the Touch.
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