Subaru 2007 Impreza-WRX Owner's Manual page 226

7-29
Starting and operating
! 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.