netlogo - How do I properly use the 'random' function for multiple agents? -

in model have agents collecting agent bump @ random after move base. move drop off material defined random function. here's sample code

to go ask searchers      [ set energy energy - 1        fd 0.0125        if random-float 1 < (1 / 50)           [ ifelse random 2 = 0             [ rt 45 ]             [ lt 45 ]           ]      search     ] end  search if any? depots in-radius vision [color = yellow] [spread set energy 0] ;; makes them base end  spread if random 10000 = 1 [hatch-rubbish 1 [ set color white    set shape "circle"   set size 0.5]]  end  

if set visual radius enormous can see depot number of bits of rubbish works out.

however if allow them move around radius of 1, count of rubbish higher 1 in 10,000.

why make difference?

thanks