On Fn- :
TRACE[xfpm-button.c:115] xfpm_button_filter_x_events(): Key press: ((XfpmButtonKey) BUTTON_MON_BRIGHTNESS_DOWN)
Could not set the value of the backlight: writing '63975' to /sys/class/backlight/amdgpu_bl0/brightness failed

** (xfce4-power-manager:4541): WARNING **: 12:34:49.865: (xfpm-brightness.c:528):xfpm_brightness_helper_down: runtime check failed: (xfpm_brightness_helper_set_level (brightness, set_level))

** (xfce4-power-manager:4541): WARNING **: 12:34:49.870: xfpm_brightness_helper_down did not change the hw level to 63975
TRACE[xfpm-manager.c:365] xfpm_manager_button_pressed_cb(): Received button press event: ((XfpmButtonKey) BUTTON_MON_BRIGHTNESS_DOWN)

On Fn+ :
TRACE[xfpm-button.c:115] xfpm_button_filter_x_events(): Key press: ((XfpmButtonKey) BUTTON_MON_BRIGHTNESS_UP)
TRACE[xfpm-backlight.c:183] xfpm_backlight_show(): Level 255
TRACE[xfpm-manager.c:365] xfpm_manager_button_pressed_cb(): Received button press event: ((XfpmButtonKey) BUTTON_MON_BRIGHTNESS_UP)

But the brightness scale of the lcd panel is from 0-255.
Current brightness is at 10, but Fn+ shows the wrong level(255).
Fn- seems to set the brightness value to an invalid brightness setting.

[shreevari@localhost ~]$ cat /sys/class/backlight/amdgpu_bl0/brightness
10