If by moving the SIGHT up you mean actually raising it by moving the slider forward to 600 yards, it is very unusual for an AK to shoot low. I want to be sure I understood you correctly. Moving the SLIDER up lowers the POI.
Sorry....I meant all the way back even below the 1 on the sights.. mine goes from nothing to 1 then 3 then 3. I have it as far back as it will go below the 1 and still shoots very low. I guess I just need to out a red dot on it but I live using iron sights
Pushing the slider forward should increase your elevation. Pushing it to the rear lowers the rear sight and will lower your Point of Impact. If it is a couple inches off at 50 yds you can screw the front sight downward to increase elevation. (Front sight is adjusted opposite of rear sight)