Extended Irreducible Binary Sextic Goppa codes

Let $n (>3)$ be a prime number and $\Bbb F_{2^n}$ a finite field of $2^n$ elements. Let $L =\Bbb F_{2^n}\cup \{\infty\}$ be the support set and $g(x)$ an irreducible polynomial of degree $6$ over $\Bbb F_{2^n}$. In this paper, we obtain an upper bound on the number of extended irreducible binary Goppa codes $\Gamma(L, g)$ of degree $6$ and length $2^n+1$.