As someone who has CCTV, I have some experience of this there are 2 types of camera, quite a few are filming all the time, but are not motion activated, this means that to see your clients coming and going, they would have to sit in front of it all day, watching it, they are not going to do this, it would take them hours.
If it is motion activated and sends alerts to their phone, so only records when someone walks past it, in this case its a total pain and they can see everything, look at the model and google it to see which type it is.