I think they forgot to test the charging process when they were producing the unit. It's wonky. When I use an external charger (a BlackBerry one), the red light comes on after 10 minutes, and then turns off after about 3 hours. I assume that it's then charged (even though that's not what the manual says).
If I unplug the Kobo while the red light is still on, then it stays on until I cycle the power.
When I unplug the charger, I get the message that Kobo is "processing new content". Then all of my "unread" items in the "I'm reading" list --- these are subscriptions from Calibre --- get moved to my Books library. I've gotta get rid of those free 100 books, because it's a pain to find 5 different subscriptions sorted into the 120 books I now have!
I like the Kobo, but behaviour like this just leaves me shaking my head.