How many questions?

So I did the API call to get the number of questions. But I can’t find anywhere that tells me which number is used for the API calls to get questions.

Is it on the verified questions?
Total Questions?
Total Questions - rejected questions?

Is there any way to become a volunteer and verify questions?

{“total_num_of_questions”:19278,“total_num_of_pending_questions”:10639,“total_num_of_verified_questions”:4146,“total_num_of_rejected_questions”:4507}

Only the verified questions are called. And no, they don’t accept volunteers. People have offered before.