Water Efficiency - Dual Flush Valve GPF Average Explanation

I'm currently working on a school renovation that's aiming to achieve a LEED Silver rating. One of the credits that we're after is Water Efficiency Credit 3 (35% water savings). We're currently achieving this with the use of .5 aerators on all lavatories, .125 GPF urinals, and 1.28 GPF water closets. Our current savings is roughly 37%. Unfortunately, we have a "master plumber" on campus that is completely against the 1.28 water closets and has the backing of the owner. Without the 1.28 GPF water closets, our chance at achieving even a 30% savings is shot. With that said, I have proposed the use of a dual flush (1.1 and 1.6 GPF) valve, and both the "master plumber" and owner are on board. I typically specify a 1.28 flush valve/fixture and I'm not too familiar with the GPF average of a dual flush valve. Could someone please explain the GPF average for a dual flush (1.6 and 1.1) flush valve to me? When you average the 1.6 and 1.1 together, you get 1.35… however I believe that LEED considers a dual flush valve to average 1.28 GPF or less, is this correct? Any information that can be provided is well appreciated. Thank you, Aaron Downing