Right, because God couldn't take billions of years to create us. He only had the strength to do it in 7 days.
God didnt create us over billions of years. He has the strength to do it in any time frame He saw fit. Which just happened to be 7 days. He can/could/will expand the universe that He created in any time He sees fit as well. We as imperfect humans may not have the capacity to understand His greatness.