I think I've got some issues with this app (n810 diablo).
I've noticed that after some time - the backlit is working at it's maximum level.
When I click on app's icon - and just point stylus at the existing backlit slider (set to ie. 30%) - the display dimms to this 30%.
Looks like it brightens up (maybe if the light sensor is exposed to the high intensity light - just my guess) with time (changing it's max setting).