Make certain that you are shooting your arrow at a level plain with the chronograph for an accurate reading. As far as the distance, just make sure that your arrow has plenty of room to clear the chronograph before hitting the target.
I love shooting the chronograph from time to time, it's the best release check there is other than having Rod Jenkins standing beside you watching. When all of your arrows are shooting within 1 fps from the same bow, your release is at the very least consistent.
One more thing, make certain that the battery is fresh. An old battery can give out some crazy readings. All of the ones that I have ever used takes a 9 volt battery.
If you still have that Horne, don't be surprised when she blows the doors off the other bows, lol.