Well, let's say we have a large amount of states computed (e.g. over 50), all with the same multiplicity.
So, our ground state can be $X^2\Sigma^+_g$ and we can continue with $B^2, C^2$ etc. as described in Molecular orbitals symmetry - states notation and Letter codes in molecular term symbols.
But what is the convention of the number of states is larger, than the number of letters? Does any convention like $B^2_2$ exist?