Please see Screenshots - GSX don´t find the Refuel Point for the iFly 737 Series. Please the Coordinates - Thanks!
That's a default refueling point, it simply means that plane come doesn't come with a pre-made refueling point. We haven't customized all the ones included in the GSX internal database, because it shouldn't be too difficult for users to add them.
Instead of trying to figure out the coordinates, just click the "Customize in 3d editor" button, which will allow you to place the refuel point visually. Have a look in the GSX manual to check which keys are used in the 3d editor.