Great at capturing velocity but changes my poi significantly - Magnetospeed Sporter Barrel Mounted Ballistic Chronograph

I purchased the Magnetospeed Chrono because I was trying to estimate my bullets' velocities based on POI at 100 yards and 200 yards but folks told me I really needed a Chrono. I didn't want to spend a ton of money and thought that something attached to the end of the Rifle barrel (versus downrange) would be much simpler to use. When I received the unit, I read all the directions and attached it exactly as instructed. Initially, I used the thinner rubber mount pad with unit set to Hi 1 sensitivity (which is what it recommends for 6.5 Creedmoor caliber). What surprised me was that my POI @ 200 yards was 4 1/2" higher with the Chrono attached than without it attached. I really thought I must have messed something up so I returned to the Range a few days later but decided to try out the thicker rubber mount pad. However, the results were exactly the same, my POI @ 200 yards was 4 1/2" higher with the Chrono attached than without it attached. On my 2nd Range trip, I initially shot 10 rounds without the Chrono, then shot 10 rounds with the Chrono (after the barrel cooled) and these were the results that I found. During my 1st Range outing with the Chrono, I thought it may have been a Scope issue but that doesn't appear to be the case. I made sure the Chrono was fastened exactly as instructed and stayed firmly in place. Folks say that I'm probably affecting the barrel's Harmonics but how do you account for a 2 1/4 MOA shift? The very last Theory I had was perhaps the Chrono wasn't level but I checked and it appears fairly level. I'm totally confused. My Velocity readings also appear a bit on the high side but I don't have any way to confirm this right now.