From the brochure available on the Keystone site, you have 67 gallons of fresh water, 93 gallons black tank capacity, and 93 gallons of grey tank capacity. I'm thinking your front bath grey tank is by itself, and your rear bath shares grey with the galley grey tank. You must have two black tanks to handle the two toilets.
http://www.keystonerv.com/media/3245...ochure2010.pdf