How, you ask? We now use both sides of any piece of paper we use (OK, except for the toilet paper). Simple math says that’s half of what we were using, hence the claim — which is about as accurate as what other businesses are claiming. “Green, Inc.”:

Each day, more companies claim to have slashed their carbon footprints or achieved other sustainability goals. But how meaningful are these claims, and are they independently verified?
The short answer: It’s murky.
In the United States, which does not yet require companies to reduce their greenhouse gas emissions, experts say there is no clear standard for reporting carbon footprints, and not every company gets their numbers verified by a third party.
“There’s a lack of standardization, and that’s the biggest issue right now,” said Eric Israel, who heads the sustainability practice at KPMG, an auditing firm.
Andrea Moffat of CERES, a group of investors and environmentalists, said that the World Resources Institute and the World Business Council for Sustainable Development have come up with a methodology for reporting emissions related to a company’s on-site energy usage.
However, she said, there is no agreed-on protocol for emissions drawn from a company’s supply chain.