LEI Electronics TXDPF9 - Manual (Page 11)

11
Contrast
This option can be used to set the screen contrast. The contrast is
divided into 15 different levels, from -4~0~4, with larger numbers
representing greater contrast.
TFT Brightness
This option can be used to set the screen brightness. The brightness
is divided into 15 levels, from -7~0~7, with the larger (positive)
numbers representing greater brightness.