There is a one-to-one correspondence between the sets of equivalent correspondences (not of value 0) on an irreducible curve of Genus (Curve) , and the rational Collineations of a projective space of dimensions which leave invariant a space of dimensions. The number of linearly independent correspondences will be that of linearly independent Collineations.
References
Coolidge, J. L. A Treatise on Algebraic Plane Curves. New York: Dover, p. 339, 1959.