Contention for M7 Motion Chip?

What happens when multiple apps access the M7 motion chip? When one app reads a step count, does it zero the counter for other apps, or will other apps also be able to access the step count and double count the steps? For example, I use MyFitnessPal and RunKeeper. At work today, while fairly sedentary, I enabled access to the M7 processor in MyFitnessPal. It tracked about 1500 steps. This evening, I went out for a walk and turned on RunKeeper. It logged my activity in MyFitnessPal when I was done, and the steps in MyFitnessPal dropped to zero. I lost the ~1500 steps from earlier in the day. What's going on?