Foliage issue

I’m new here, so sorry if I make mistakes (Kind of ignorance of anything).
I apologize for my English language. Google translator

But to the point. I design a game, and I want to add elements of the environment, grass, trees, etc.
I do this by painting Foliage, and everything goes well, ie objects appear on the map surface, only in some radius from its center. But when I move to the edge of it, then the brush does not want to paint it. But the hand models of this grass, trees, or I can put on the site.
So my question is.
Are there any settings that limit the brush? Or something like Kill Z?
Thank you for any help.

Yes, check here: