World Boarder being slightly off the 30mil mark

The worldboarder is off the world limit by a little bit. The coordinates of the worldboarder corner is at x: 29999983 y: x z: -29999983 instead of x: 30000000 y: x z: 30000000 although it says that the world boarder is currently at 60000000 blocks wide. In reality, it's only 59999984 blocks wide if you do the math