Follow the steps to get the correct coordinates.

1. Go to X:0 and Z:0 (Press F3 to show coordinates)

2. Throw an ender eye, look at the center of it and look at 'Facing' Section.

Write down the Facing (North,south,west or east) and the first number after it.

E.g: Facing: north (Towards negative Z) (xxx <- this number)

Write that number here. (The most you look to the center of it, the most accurate it is.)