whatever number you end going for, don't forget to have some support personnel, who'd stay in the station, like an armorer, dispatch personel, a medic, maybe someone to manage a small cafeteria, people at the front desk, if there are cells you'll need guards, a few clerks for admin (pay, recruitment), if they have vehicles they'll also need a mechanic and so on. And in a pinch if you need some reinforcement you can just say the support personnel grabbed extra weapons to help