Distance mistake

Hello again, dear support.

I continue testing my site and I have seen a mistake (I think it is a mistake) in the distance that is displayed in the geodir search result page when I look for a place writing another place in the near to field.

I have realized that that distance is different of the distance that you get if you perform the same search in google map, or even in the detail page of the place using the “How to arrive” button just down the map. In the case I have seen the real distance by google maps is “120 kms” and the distance in the geodir search result is “87,7” kms

Is there any explanation of this? Is it a mistake or a different way of doing the calculation?

I have checked that I am using kms in geodirectory and google maps, so it´s not a mistake of different measurements units.

Please, tell me something about it. I think is a very big difference over a very short distance.

Thanks in advance