Cycle Computer Does Anyone Know How To Set Up A Halfords 8 Function Cycle Computer?

Does anyone know how to set up a Halfords 8 function cycle computer? - cycle computer

I have (even a new battery for my team, Halfords 8 Function cycle around 1997) and as I long since lost the instructions I have no idea how to set the wheel size. The device itself has two buttons on the right side, through the various functions and the left side seems to do nothing. If both buttons may be held on time can be programmed. Is that a standard configuration for this type of device, and therefore a generic form, from which they were created?