React useEffect Hooks with setTimeout

Question

I am so confused here with React useEffect Hooks with setTimeout. 

but my code is rendering "I've rendered 2 times" instead of "I've rendered 1 time". And I have tried it in many code editors, and mine always shows 2..

My: 

And the only way I can get it to render 1 is refactoring to this instead

useEffect(() => {
     setTimeout(() => {
     setCount(count + 1);
   }, 1000);
 }, []); 

Could someone please explain to me why? Thanks for your help!

I am expecting my code to render the same result as the w3school example.