If you log in on thehunter.com (or the steam launcher) go to your profile page (right-top of the screen) you have a tab called "achievements".
When you click on it go to the "exploration" achievements.
There are 2 rows, one is for the distance walked and the other one for the hunt duration total.
If you hover over one of those rows it says "achievement-title-number".
This is for both rows.
i quess this should be "distance-25km walked" for example.
Here is the location of the bug in a image:
Spoiler:
It's a small bug, but maybe the dev's can fix it