It depends on your plan. Each of your games can have:
- Free: 5 rivals
- Indie: 25 rivals
- Studio: 100 rivals for each of your 5 games
The Rivals page shows how many slots you have used. When every slot is taken, remove a rival to make room or upgrade to watch more.
Tip: on Free, keep your slots for the games closest to yours. They are the ones that matter most for your launch week.