I asked our Devs, and Kevin Montrose Responded with:

(# of new questions over last 14 days) / 14

There might be a little cache delay, but that is roughly it.

I asked our Devs, and Kevin Montrose Responded with:

(# of new questions over last 14 days) / 14

There might be a little cache delay, but that is roughly it. Questions doesn't count deleted questions, but it does count closed questions.