XPS 13-9370 Cannot adjust Brightness on Battery vs Brightness on AC in Bios

Hi, My 9370 cannot adjust the LCD Brightness on Battery vs LCD Brightness on AC in Bios Setting. The "Apply" button is grey and cannot press or save. It always come back to default setting that make the brightness on battery is higher than on AC. BTW, with default setting in BIOS, the brightness control also seems does not work in win 10 because the LCD keep the same brightness level when I plug in & out. I'm with the newest BIOS updated by Dell. Thanks,