Google, internally, is pretty up front that there's a forced distribution (or quota) for performance ratings and promotions. It's for budgetary reasons, and it'

Google, internally, is pretty up front that there's a forced distribution (or quota) for performance ratings and promotions. It's for budgetary reasons, and it's not strictly enforced, but it's published and often referred to. Past a certain level, a business justification is also needed in addition to merit. The quota the manager was referring to was very likely that.