Notice that there are small colored arrows beneath each of the densitometer's keys. One key has a blue arrowpointing down. The another key a red arrowpointing up. The third key two arrows; a blue and a red. To edit the displayed value proceed as follows:
Incrementing displayed value
Press and HOLD the key with both arrows. While holding this key, tap the red arrowed key to increase the displayed value.
Note that you can quickly raise the displayed number by holding this key down. The number will increase slowly at first, but will accelerate if the key remains pressed.
Decrementing displayed value
Press and HOLD the key with both arrows. While holding this key, tap the blue arrowed key to decrease the displayed value.
Note that you can quickly lower the displayed number by holding this key down. The number will decrease slowly at first, but will accelerate if the key remains pressed.