Nokia Betalabs

Step counter is not calculating distance correctly. For example, my step length is 88 cm, so when i run 8302 steps, the distance have to be 7.30 km and not 8.61 km as it shows. I've tried several times, with other distances, but the software keeps giving me a number bigger than it should be. My phone is a n95 8 gb, firmware v 20.0.016.