Subaru Legacy 2002 Service Manual page 2196

STOP LIGHT SWITCH
Brake
D: ADJUSTMENT
S405542A01
Loosen the lock nut, and adjust stop light switch
position until the clearance between threaded end
of the stop light switch and the stopper becomes
0.3 mm (0.012 in). Then, tighten the lock nut.
B4M0617E
BR-57