Put 5 requests into random controller and only 1 req will be executed at a time.Make loop count to 5 and 5 reqs will be executed,but they might be repeated that is in a loop count of 5 any req can be repeated twice etc.

If we click ignore sub controller blocks then if we put a simple controller within this random controller and put some reqs into it then only 1 of those reqs will be executed even if the loop count is 10.one can be executed twice,thrice whatever but not both.If the tick box is not clicked both can be excuted once,twice etc.