Codimension of polynomial subspace in $L_2(\mathbb{R},d\mu)$ for discrete indeterminate measure $\mu$

A calculation formula is established for the codimension of the polynomial subspace in $L_2 ({\mathbb{R}}, d \mu)$ with discrete indeterminate measure $\mu$. We clarify how much the masspoint of the $n$-canonical solution of an indeterminate Hamburger moment problem differs from the masspoint of the corresponding $N$-extremal solution at a given point of the real axis.