How winding number in a boundary point of a curve is defined?

Question

We know that, the winding number counts the number of rounds of a curve around a point. It is a positive integer for positive oriented curves and a negative integer for curves with negative orientation. If the point a is enclosed by a simple closed rectifiable curve, then n(γ, a) = 1 and, if a is outside the curve, then n(γ, a) = 0.But if the point a is on the boundary of γ then what is n(γ, a) ?