Basically, when you are near the basket, Jump Shot is very important and Jump Range isn't really required. But as you get further away from the basket you need higher Jump Range to still make the shot.
So a player with 15 JS and 3 JR will shoot well when he is close to the basket, but will be absolutely horrific from the 3 point line. On the contrary, a 10 JS and 10 JR player will shoot pretty good when he is close to the basket, and pretty good from the 3 point line.
Does that make sense?