these are positive real numbers representing a size, which can only be positive.
direction is irrelevant.
the absolute value of an imaginary number is the distance of that number from the origin on the imaginary number plane. it does not matter in what direction.
the magnitude of a force is just the power involved, it does not say what direction.
the distance between 2 points - that is the same case as with the absolute value of the imaginary number. a distance is always positive independently of the direction.
