setHealth issue

[ProjectSky]

i use the following code to modify zombie health, but i found some issue.

 

local zb = getPlayer:getCell():getZombieList()
if zb ~= nil then
  for i = 0, zb:size() - 1 do
    if zb:get(i):getHealth() < 2 then
      zb:get(i):setHealth(ZombRand(5.0, 10.0))
    end
  end
end
    

When I kill these zombies, the information panel shows that the number of kill zombies  keeps increasing.