Important that I mention: The car's battery was faulty. The car kept failing to turn on except for at random times when it would actually work. When it failed, the car would shut off and the battery would be very drained. The dealer fixed this by replacing a part of the battery. The car turns on reliably now.
That light, however, came on as soon as the car was turned on (actually turned on for once) and driven over to the dealer for the battery issue alone.
It's also important that I mention that my father was trying to install a battery tender which involved loosening the nuts on the battery to connect the tender. However, they were retightened afterwards. They were certainly not loose.