Does this also apply to solo mode, no server, just local save data?

I've dug out a fairly big island and the highest instance count for me is 4300. Now the base itself is not huge but is has a lot of detail to it, and I did do a fair amount of terrain editing.

I wonder where my limit is. I still haven't seen any fps drops in and around my base.

An other base that I built on on a different map has a base three times the size. Instance count over there is also 4300?

Not sure how this works.