I really dont remember how math.random works but it is something like this:
local stonePos = {
{x=1234,y=1234,z=7},
{x=1235,y=1234,z=7},
{x=1236,y=1234,z=7},
{x=1237,y=1234,z=7}
}
local stoneRemove = math.random(stonePos)
doRemoveItem(getThingFromPos(stoneRemove).uid)