Anti-servo Tabs
An anti-servo tab works in the opposite way to a servo tab. It deploys in the same direction as the control surface, making the movement of the control surface more difficult and requires more force applied to the controls by the pilot. This may seem counter-productive, but it is commonly used on aircraft where the controls are too light or the aircraft requires additional stability in that axis of movement. The anti-servo tab serves mainly to make the controls heavier in feel to the pilot and also to increase stability .
On some aircraft with stabilators (all-flying stabilizers) an anti-servo tab acts as a trimming device. In this use some manufacturers term it a "balance tab" or "anti-balance tab".
Read more about this topic: Servo Tab