finally an explanation between "As" and "Bs"

But it still leaves a question for me.

In Season 9, when Rick leaves, and Jadis/Anne is on the walkie with the CRM chopper, the way she says "I have a B, I never had an A" makes me wonder. The way she says it implies to me that they want As, but she's hoping they'll accept a B. But we learn here that they more want Bs. And if they're killing off As, why would they want As at all to begin with?