Advertising will come whether Brave tabs are open or closed. Brave will run in the background. Also, what type of advertising are you looking to see? Brave’s ads are served as notifications on your device. So if on Windows, it serves in your Notification Center on the bottom right of the screen. If you’re on Android, it serves in Notification Center on the top of the screen.
10 per hour setting is the maximum you can see. There is no minimum guarantee. There are a lot of things that influence how many ads you see. The primary thing though are how many campaigns are in your area and whether those campaigns are targeting your OS. You can learn a bit more about that at Understanding Brave Ads Catalog Viewer
What do you mean on this? Are you just saying less than the 10 per hour you selected? Are you saying you’re not being paid for ads you see? Or what specifically is meant here? I want to make sure I’m seeing it right and giving you a proper answer.