Slowtan, this post has some info on Goldline SWCGs not giving the right salt #. Use the diagnostic button the check instant salinity (push #5).

I suspect that your unit may be identical to the AquaTrol model and has a timer built into the box - even though you're not powering the pump via the box the unit will only generate (and update the salt display) when the timer is on - this would explain your current problem