Looks like there is a mistake in the article. The new plane will "burn 70 percent less fuel than a Boeing 737", however, the numbers immediately below indicate that it will actually burn 70 percent of the fuel a Boeing 737 does - 30% less fuel.
Also, as a rule of thumb, fuel consumption per unit distance is proportional to speed squared. According to the chart, the "Double Bubble" cruises at 490 MPH, while the 737 cruises at 596 MPH. The "Double Bubble" achieves 145 MPG, while the 737 achieves 100 MPG.
(490/596)^2 * 145 MPG) = 98 MPG
737s are already on the slow end of airliners, but it seems like all the fuel savings in this design study come from just flying slower.
I believe (depending on the config)a 737 burns 850 to 2000 g/hr. Wide range based on if it's the 737-400 or a different variant, if it's climbing, fully loaded, etc.
It is not, however, near what is stated in the info graphic.