Inaccurate

I used the free version of this app and decided to purchase the paid version to keep track of my walking for more than 3 days. I measured the distance with my car to see if the app is accurate. The free app is accurate and the paid version is not. There is a big difference between the # of steps and distance. The only thing that is accurate is the time. I ran both simultaneously this morning. They were completely different except for the time. WHY?

Caper-52 about Pedometer Step Counter PRO by Runtastic, v2.3.1