Screen Brightness only 30%

Hi

I want to control the screen brightness from a tablet.
The following service is working, but only to about 30% of the maximum screen brightness.

service: notify.mobile_app_wkrr
data:
  message: command_screen_brightness_level
  data: 
    command: 255

Are there any restrictions, that I have to turn off, to reach maximum brightness?

Same result with Fully Kiosk
If I set the brightness on the mobile phone, I see 803% on the light entity

I couldnt find any workaround!

In Fully Kiosk Browser in “Device Management/Screen Brightness”, I can set value 2047 to get 100%.
How can I send this value via HA service - max value there is 255

Make sure you don’t have automatic brightness enabled.

I tried both automatic brightness enabled and disabled.
After changing the brightness to 255 via HA, the result is the same (~30% brightness on the device)