How could that be? Well, those $700 billion were in ObamaCare, and Ryan and the Republicans repeatedly voted to repeal ObamaCare--which includes those cuts!! Maybe that's a bit complex, but it makes sense that context:
Since the Medicare cuts were part of Obama's health care law, Republicans included that projected spending in their proposal, Ryan said. He justified it by pointing out that the House later voted to repeal the health care law, which would have stripped out those cuts, and said that Republicans never proposed them.
"First of all, those are in the baseline, he put those cuts in," Ryan said, referring to Obama. "Second of all, we voted to repeal Obamacare repeatedly, including those cuts. I voted that way before the budget, I voted that way after the budget. So when you repeal all of Obamacare what you end up doing is that repeals that as well."