New Computer Installation

I have recently purchased a new CatEye computer for my bike.
In the past the computer that I have installed stated in the
instructions that the magnet should be placed as close to the
axle as possible. With my new computer the sensor/magnet is
placed about midway on the fork. Nothing in the instructions
state how high or low on the fork the sensor should go. If
the sensor is placed at a random height, won't this throw
off the accuracy of the computer? If the magnet is not
placed as close to the axle as possible, won't this throw
off the balance of the wheel?