Hi muiz6849, you can try to double tap on the Always On Display area when your screen is off to manually adjust its brightness. If you have tried and it works, feel free to click "Accept Solution" on top right corner of my comment. Thank you.
I tried double tap on the AOD clock but there is no brightness setting there.. Only Settings shortcut appeared which opens the AOD setting.. I don't see any option to adjust the brightness..
I see. I think the option to adjust the brightness is not available in your device model, but I believe Always On Display really looks good when it is on high brightness. Even my Always On Display is set to the highest brightness to make it more seen in bright places especially outdoor. If you feel afraid that the Always On Display will consume your battery life too much, fret not as it consumes really small percentage of your battery life even after a long hour 👍