Here you are. For me, first two value are 0 or 1, third is just "%extradim".
Note: I did find out that it doesn't affect all Secure Settings - this one seems to be Samsung-specific. But nevertheless, the list for "Select Setting" shows the name and value correctly (I checked that it's actually changin), and I can change the value with no problems.
Task: Test Custom Setting
A1: Custom Setting [
Type: Global
Name: adb_enabled
Read Setting To: %adb ]
A2: Custom Setting [
Type: System
Name: blue_light_filter
Read Setting To: %bluelight ]
A3: Custom Setting [
Type: Secure
Name: reduce_bright_colors_activated
Read Setting To: %extradim ]
A4: Flash [
Text: ADB (G): %adb
Blue Light (Sys): %bluelight
Extra Dim (Sec): %extradim
Tasker Layout: On
Continue Task Immediately: On
Dismiss On Click: On ]