GameLift server processes metrics intermittently higher than configured concurrent processes

Hello,

Our fleet is configured to run a single instance with 4 Concurrent processes. However, the metrics for Active server processes, Healthy server processes, Available game sessions, and Concurrent activatable game sessions all intermittently bounce up to 8 and back down to 4. There's no traffic on this fleet at all during this time, it's idle.

Here's a screenshot:

I logged into the instance and ran ps to check the actual processes, and there's only 4 as expected, and all of their start times match the start time of the instance, so I don't think processes are stopping and starting during this time.

What could be causing this?

We're using GameLift SDK version 5.1.1, for reference.

Thanks!

Allan