Ok what am I not understanding about this? I bought this cartridge, and strangely you replace the BLACK ink one with it, and not the colour. Ok so I do that, and then the colour cartridge depletes almost immediateky and the meter says the photo ink is still full. So I then tick the checkbox "print in black and white" assuming that only ink from the photo cartridge is used and still the colour ink is runnig out.

What am I not doing right?