The red light can take an extremely long time to get started if the device is completely flat and you are charging via usb. And if your computer goes to sleep or hibernates, then it will stop charging altogether.
It takes a few charge cycles for the battery meter to calibrate itself properly, so new devices can display an inaccurate battery meter. This should sort itself out after a couple of charges.
We have a thread on mains charging (which I prefer):
https://www.mobileread.com/forums/showthread.php?t=56170
and on usb charging:
https://www.mobileread.com/forums/showthread.php?t=56170