Why is my S Health calculating the wrong mileage when I'm walking

[AC Question]

Iwalked 3 1/2 miles this morning it only shows that I walked 0.39 miles which is totally incorrect
It should read 3.39 miles. How can I correct the problem the calculation is way off(S heath app

 

[the tall guy]

Hi, do you have your location on the phone set to the highest setting? also where do you keep the phone when you are walking? it might not be picking up the steps if you keep it in a bag or something similar.