Minolta X70 SLR Camera

Question

We needs manual or any informaton that could be relavent to this camera: Minolta X70 SLR Camera. More to do with the buttons or light meter setting, the + - that is written on one of the controls of the camera. It says +1 or -2 and some more numbers and we would like to know what you use it for. Any help would be greatful and widely appreciated. Thank you.