Is anybody experiencing their steps and Miles not adding up

I have emailed this app several times and it's very frustrating I recently discovered that for example 6.1 miles according to the step app is only 6, 809 steps but if you Google 6.1 miles it's around 12,000 steps so you tell me that seems an awful weird I had this app over a year or so ago and I had no problem getting to my goals as far as gift cards I have yet to be able to claim a gift card and I walk a good 6 miles a day when I work and I have yet to be able to redeem a gift card for five bucks that's crazy