The value is shown in a scan (at the journal event) of the Sol star system, where the Earth has a value of 9.797759 m/s² stated for the gravity.
So the value comes directly from the game and so I think it is the base for all gravity values for all planets in game.
Gravity values in real depending on your location, where is was measured, pole region has a higher value than the equator region for instance.
so much for a 1:1 copy of our real solar system... hehe
Of course, it could also be that they're accounting for the eventual slow-down of Earth's rotation, which does affect gravity.