How do I adjust the screen brightness on my TH6210U2001, TH6220U2000, TH6320U2008?

Note this does not apply for the RTH6330. 

Brightness options and Brightness levels are in the ISU settings.

1. Press and hold CENTER and + buttons for approximately 3 seconds to enter advanced menu.
2. Press Select to enter ISU.
3. Press Select to cycle through menu setup options.
4. Press + or - to change values or select from available options.
5. Press Select and confirm your settings or press Back to ignore changes and return to ISU menu screen to continue editing another setup option.
6. To finish setup process and save your setting, press Home and return to Home screen.

ISU 1400 and 1401 cover screen brightness.