It seems to control the maximum leaf connections when in Ultrapeer mode .
I tried setting it on 10 and LimeWire didn't make mre then 10 leaf connections (other connections not included) .
Where i used to have up to 50 leaf connections i now have only 10 anymore .

I'm gona put it on 20 from now on .

Very usefull , if you are not afraid to experiment a little with LW you can bend it every way .