2003 Subaru Impreza Owner's Manual - Page 260

Starting and operating 4 mph (6.8 km/h), the vehicle speed will be lowered by 1 mph (1.6 km/h). This occurs because the cruise control system unit regards this lever operation as that intended to decrease the vehicle speed. B To decrease the speed (by control lever) Push the control lever downward in the "SET, COAST" direction and hold it until the vehicle reaches the desired speed. Then, release the control lever. The vehicle speed at that moment will be memorized and treated as the new set speed. When the difference between the actual vehicle speed and the set speed is less than 4 mph (6.8 km/h), the set speed can be lowered 1 mph (1.6 km/h) each time by pressing the control lever downward in the "SET, COAST" direction quickly within 0.5 second. B To decrease the speed (by brake pedal) 1. Depress the brake pedal to release cruise control temporarily. 2. When the speed decreases to the desired speed, press the control lever downward in the "SET, COAST" direction once. Now the desired speed is set and the vehicle will keep running at that speed without depressing the accelerator pedal. - CONTINUED - 7-31