Seems ok to me, they don't make it, just supply the specs given by G&G.
Quoting range is always a bit iffy but it makes no difference to the product.
One you get it DJMK4 i would go around making sure any loose screws are torqued up and clean the barrel, i've bought rifs with barells full of packing grease and all sorts (you should get a cleaning rod with it, if not they are a bastad to find seperately).
You will want to get some silicone spray (as it won't corode the hop rubber). Spray that on the cleaning tissue and run it through with the rod (be very careful of the Hop rubber at the bottom end of the barrel), if dirty, change tissue and repeat, once there is no trace of dirt on the tissue run a few dry ones through to clear out the silicone residue.
After that you will want to tune your hop. There will be a little wheel in the ejection port with an arrow showing which direction for hop. Too little and it won't go very far, too much and it will either sky rocket or jam in the barell. A good range is 50-60M.
obviously be careful where you are testing it, if it's in a garden visible by neighbours you may want to inform them. I have mates who have had a knock on the door because of nosey neighbours.