Gas Line To Stove

I have removed the Atwood cooktop/oven combo from the camper (we never used the oven and I am installing drawers in the space) and will be installing just an Atwood gas cooktop. The gas line connects exactly the same way. My question is how do I correctly remove the gas line? In the picture you see a large nut and a smaller one. What is the proper way to unscrew this connection?