.Map :: MoHAA Mapping

I have compiled my map and created a log, however there is somthing in the map that i am unsure as to what exactly it means. Can someone please tell me what they mean, if its a prob and how to solve it.

This was in the vis_log:

farplane - 132 of 170 portal mega-calls culled, 77% effective

Thx in advance

Uh well that more or less tells you how effective your fog is for improving fps.