A friend has one that we use. He first had the short range system and it did good to go 400 yards. He traded it in for the long range system. We have used it to 600 yds. with no problems. It works best with a laptop or note pad over a cell phone.
Set it up at your target and get the signal on your computer all set up. Then drive to where you are going to shoot from.
It's like most things, the more you use it, the more you learn about it. If you don't use it all the time, you forget how to use it. Keep the batteries charged!