If you know much about archery then you are aware a 9 yard difference can be huge.
The measurement of the actual range in which gravity will have an effect of your arrow. The actual range will change with an up or down angle, and the steeper the angle you are shooting the more drastic the difference will be.
Example: One Mule deer I took was 37 yards away from me below a cliff. My Bushnell Rangefinder told me to shoot for 25 yards, which I thought was a little much. I choose to shoot for 30 and ended up hitting high. I still got a pass through upper lung shot and he did not go far, but had I aimed for where the range finder told me to, my shot would have been spot on. The picture of the buck at the beginning of this page is the buck in this story.
There are many different scenarios we bow hunters can find ourselves in. While hunting out of a tree stand 20 feet off the ground, the true horizontal distance might not have enough effect to really need a range finder with an angle compensator. The thing is, you do not want to find out if there was much of a difference in point of impact after the shot. The only thing worse than a clean miss is a dirty hit!
One thing that throws people off a bit is the fact that regardless of if the target is up or down hill from the archer, the point of impact will be high. This is because the actual horizontal distance is the same whether it is an up or down angle of the same distance. This is very difficult to explain, but if this does not make sense, please just take my word for it: If shooting up or down angles, the point of impact will be high.
If you are new to bow hunting, then you are in for a special event. Just be ready for discouragement as it is amazing how many times you can be within spitting distance and still not get a shot. If you have been bow hunting before then you know about the excitement and challenge. No matter how much you bow hunt, there will be a lot to be learned as every scenario will bring up different challenges. One of the best tips I can give that was learned form experience it to always use and trust your rangefinder.
If you have ever tried bowhunting without a range finder, then you know how quickly bow hunting can become a guessing game. Even though range finders for bow hunting take away a part of the challenge of shooting off instinct, the importance of making a clean kill shot far out way the ethics issues that some people associate with modern day bow hunting.