Hello,
If you mean IoT-installation as in "Installations" in the platform the answer is that at the moment an installation in the platform is limited to one connected edge client (Gateway). We are working on features that would allow several edge-clients to be connected to one installation but this is not ready for use yet.
If you are wondering about the theoretical limits of a platform and amount of installations that can be created there are none at the moment. Some tests have been done where we simulated 10 000 Gateways connected to the platform and sending data frequently.