I am currently using precision trolling app and say if I want to reach a certain depth i'm really not too sure what feet back means. What I did was let out that number of line then attached my offshore board at the tip of my rod and then let out another 50 feet or so and travel that 1.8 -2.0 mph according to the GPS. With no luck if anyone could take a few minutes and give me some instruction that would be great