Code for my Rover 75 Harmony radio (Phillips)?

I have recently bought a Rover 75 and the battery needed a re-charge. Now the display on the radio ask me for the code. I contacted the previous owner, who was not sure of the correct code. He gave me a 4 digit number starting with 8, however, the push buttons on the radio only goes from 1 to 6, so I doubt I got the correct code. Can anyone help me here?
The radio is a Harmony by Phillips and the chassis no. is RG 745WX1041097, a label on the radio top shows 3111115317 and a handwriting: 145222