Sounds like the OP has resolved his question with it only having one grey tank and a monitor that has the ability to monitor 2 grey tanks.
Our TT has 2 grey tanks (and a matching monitor panel) but the forward of the two tanks is solely for the washer/dryer prep package and has never had a drop of water in it. The rear grey tank takes the water from the kitchen, bathroom sink and shower. If we ever do much boondocking I will get an externally mounted valve on the sewer outlet that will allow for the two grey tanks to be floated together to double our capacity.