Dim display(AC)

Specifies the period of inactivity before Windows automatically reduces the display brightness and the brightness level when the Dim display setting takes effect after the specified period.

You can specify the period of inactivity in seconds.

Dim display after(AC) :

Registry Hive	HKEY_LOCAL_MACHINE
Registry Path	Software\Policies\Lenovo\PWRMGRV\PowerPlan
Value Name	DimDisplayTimerAc
Value Type	REG_DWORD
Default Value	60
Min Value
Max Value	4294967280

Dimmed display brightness(AC) :

Registry Hive	HKEY_LOCAL_MACHINE
Registry Path	Software\Policies\Lenovo\PWRMGRV\PowerPlan
Value Name	DimDisplayLevelAc
Value Type	REG_DWORD
Default Value	0
Min Value
Max Value	15