You will leave it in all night and take it out in the morning. I think one night I left it in for 10 hours. That's why you have to make sure to take the acidophilus. I never got any infections btw.
DH's sperm count is 14 mil so it's not extremely low but is considered low. Your DH's sperm is pretty low, but I still think the instead cups will help. You just need to make sure you don't get up and let any drip out. Get your husband to stick in for you. My husband made sure none of it dripped out (sorry tmi). Also, only BD every other night since his sperm is so low. So when you quit bleeding get to it and don't stop until you know you have Ovulated. Remember it only takes one little sperm so it's possible even with 400,000....
I see you're on 16 cd, right?