Pasha, why does it even matter? The only thing that matters here is that the additional workload they are trying to process requires more than 1 remaining instance, so it could only be a server (as only servers require more than 1 instance, specifically 3 instances).
Raf, it sounds like you're using the Community Edition, which is limited to 10 instances maximum. If you want to protect more workloads than you're already protecting, you should get a license for the appropriate number of workloads.