It's charged. One of mine has this exact problem, and I emailed innokin, who said it was a software issue, but not dangerous. Here're their exact words:
'if the devide has been charged a long time then like this, that means the battery is fully charge. Just the program makes a mistake on judging the result of charging, that will not affect using'
They also told me 3-4 hours is enough, no matter how discharged it is.
Ah okay, thank you!