Straight from the manual

Touch panel models
(1) Press the [8] key twice in the initial
state of maintenance mode. "RB" is
displayed on the LCD.
(2) If you press the [˄] or [˅] key, item
changes as below in Table 1.
(3) Press the [SET] key while "RB" is
displayed on the LCD.
"PartsReplacement" is displayed on
the LCD.
(4) Press the [SET] key while
"PartsReplacement" is displayed on
the LCD.
(5) Press the [˄] or [˅] key to display the
part with the counter to be reset on
the LCD, and press the [SET] key.
(6) "*******OK?" is displayed on the LCD.
Press the [SET] key to reset the
counter for the selected part and
return the display to step (2). (*******
represents the name of the selected
part)
(7) Press the [X] key, and the machine
returns to the initial state of
maintenance mode.

or

(1) Press the [8] key twice in the initial
state of maintenance mode. "Reset-
Laser Unit" is displayed on the LCD.
(2) Press the [˄] or [˅] key to display the
part with the counter to be reset on
the LCD, and press the [Mono] key.
(3) "*******OK?" is displayed on the LCD.
Press the [Mono] key to reset the
counter for the selected part and
return the display to the procedure (2).
(******* represents the name of the
selected part)
(4) Press the [X] key, and the machine
returns to the initial state of
maintenance mode.

Depending on firmware