Need help with Singles glossary

Can somebody give me a quick lesson on how the singles glossary is supposed to work?

For instance, if I view my singles glossary, the entries under A are about, again, and and. But if I type an a, only about shows up in my advisory list.

Same with B. My entries are before, better, and because. But if I type a b, only before shows up in the advisory.

How is this supposed to work?