Most folks measure the number of pellets in a 10" circle at 40 yards. A nice even pattern with anything better than 100 pellets in that circle is considered a pretty decent pattern. There's a pretty good sticky on top of this forum that explains how to do it. Good luck!
You need to shoot and check the patterns at different distances and see just how much and where the patterns shift.If you have a recoil reducing rest or know someone who does this testing will be much more comfortable.