title: FlinkKafkaConsumer watermark chart legend
body: <p>I'm trying to understand this picture <img src="https://ci.apache.org/projects/flink/flink-docs-release-1.11/fig/parallel_kafka_watermarks.svg" alt="image" /> from <a href="https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_timestamps_watermarks.html#watermark-strategies-and-the-kafka-connector" rel="nofollow noreferrer">https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_timestamps_watermarks.html#watermark-strategies-and-the-kafka-connector</a></p>
  <ul>
  <li>what does white rectangle with text like <code>N|39</code> in it mean?</li>
  <li>what does yellow rectangle with a number in it mean (with or without black boundary)?</li>
  <li>what does text like <code>W(33)</code> mean?</li>
  <li>what does dotted black lines near <code>W(17)</code> mean?</li>
  <li>What does the number in grey circle mean, i.e. the <code>(1)</code> or <code>(2)</code> under Source, map, or window.</li>
  </ul>