This statistic shows bytes that were evicted from the ZFS ARC, as part of its usual housekeeping. The breakdown allows L2ARC eligibility to be examined.
An understanding of ZFS ARC internals may be required to properly interpret this statistic.
This could be checked if you were considering to install cache devices (L2ARC), as this statistic can be broken down by L2ARC state. If L2ARC eligible data was frequently being evicted from the ARC, then the presence of cache devices could improve performance.
This may also be useful to check if you have issues with cache device warmup. The reason may be that your workload is not L2ARC eligible.
If there are ARC caching issues on the appliance, also check the Cache: ARC accesses statistic to see how well the ARC is performing, and the Protocol statistics to understand the requested workload. Then, check the Advanced Analytics Cache: ARC size for further details on the ARC behavior.