After one click, what value does this counter display?

Direct answer

After one click, the counter displays 1 because all three calls calculate the replacement value from the same count snapshot.

Counter.jsx

function Counter() {
  const [count, setCount] = useState(0);

  function handleClick() {
    setCount(count + 1);
    setCount(count + 1);
    setCount(count + 1);
  }

  return <button onClick={handleClick}>{count}</button>;
}

Output

After one click:
1

During this handler, count is still 0. Each call therefore queues a request equivalent to replacing the state with 1, rather than adding three independent increments.