All you did is scale your object non uniform in object mode. Just press Ctrl+A in object mode and apply the scale, then recalculate the normals in edit mode.
To see what happened:
Create a cube. Go to edit mode, rotate it by 45° and turn on normals.
Go to object mode, scale the cube in object mode along one axis only by factor 2.
Enter edit more again. All normals are askew.
If you go to object mode again you´ll see that the scale is 1 for two axis and 2 for one axis.
Now apply the scale with ctrl+a. You´ll see that the object now has a uniform size of 1.