Check the display cable for the three digit VCOM number.

For example: -2.81

If your screen doesn't have a printed VCOM number, scan the QR code with a dedicated QR scanner app to generate the number. Your smartphone's built-in camera app might not work.

The VCOM number registered on your eReader will be this three digit number multiplied by 1000.

For example: -2.81 x 1000 = -2810