Calculated Industries 6414 - Manual (Page 11)

1) Press the [RESET] and [Set] keys at the same time. You will
see this display (level 4 is the default setting):
2) While holding the [RESET] key down, press the [Set] key
to advance the contrast level to the desired setting (1-7).
3) When you have found the contrast level you want, release
the [RESET] key. Press the [RESET] key again to exit the
contrast level mode.
9 – User’s Guide