Activating "power saver" actually reduces remaining battery life

For me activating the battery saver from the taskbar always sets me back, for example: If I have around if 56 minutes remaining then activating power saver would probably set me back to 48 minutes remaining.

And the brightness does reduce which is strange. Why would this reduce my batter instead of saving it?

Have you tested it by letting it run and see what the ACTUAL time left is? , those 'time remaining' calculations are known to be a little bit 'squirly' when system states change, they're really only guestimates.