SRAM GX vs X7 rear derailleur

Hi! I ordered a new 2017 Marin Gestalt 2 (https://www.marinbikes.com/gb/bike-archive/bikes/2017-gestalt-2) from a shop. The bike was supposed to come with an SRAM GX rear derailleur, but arrived with an X7 derailleur. I know GX replaced both X7 and X9, but is GX closer to X7 or X9? Did I get an...