If you're asking with respect to what number it would be 0.
On a number line, a number, b, is located the same distance from 0 on the number line as -b as well.
For eg 4 is located 4 units to the right of 0.
While -4 is located 4 units to the left of 0.
The amount of units or distance is the same, only the direction is different.