I can get rain to work but only in a small area. How did you get your whole map coverd?

My map is from top view in radiant 2560 to -2560 L to R and 2880 to -2880 T to B how do I make it rain the full radious to the 0 deck from 640 height?

NOTE: you may have to edit the figures, 2548,0,27000,0,1100), 3) ect to your own map referance Grids.

How do I find out the numbers to make it rain all over my map?