Variational method: Hydrogen atom ground state in STO-3G basis expansion

I computed numerically the ground state energy of hydrogen by variational procedure, firstly expanding the wave function over the s-wave basis set STO-3G
$$\psi(r)=\sum\_{i=0}^3 C\_{i} e^{-\alpha\_ir^2}$$
and then solving the generalized eigenvalue problem (in matrix notation)
\begin{equation}
\textbf{HC}=E\textbf{SC}
\end{equation}
As output I have all 3x3 matrices. $E$ is a diagonal 3x3 matrix and my eigenvalue is the smallest of the three on the diagonal.
My question is: what do the other two elements in the $E$ diagonal represent? 


