Right but we know he didn't absorb all of it. He was feeding on Hyperstorm to a possibly endless degree. We know Galactus didn't finish eating him because Jon is one with Hyperspace and Hyperspace still exists since it's the central conduit for all fundamental elemental forces of reality (gravity, electromagnetism, nuclear fusion) that all still exist and function properly. Reed even assessed that Galactus would probably continue feeding on Hyperstorm for eternity because it's so vast. So it's safe to say Jon either escaped or is imprisoned as food rations for him.