semsets = 3

What does this mean? What do I do about it?

A -semsets of 3 is the default value indicating it has likely not be set intentionally.  It should be tuned to your specific environment.

ProTop recommends one -semset per 50 users as a best practice.

It is used in *nix and Windows environments.

Read more about Why and How to use Muliple Semaphore Sets.