Why does one structured query run multiple SQL queries for each batch?

Question

Why is the following structured query triggering multiple SQL queries, as can be seen in the tab of the UI web interface?

import org.apache.spark.sql.streaming.{OutputMode, Trigger}
import scala.concurrent.duration._
val rates = spark.
  readStream.
  format("rate").
  option("numPartitions", 1).
  load.
  writeStream.
  format("console").
  option("truncate", false).
  option("numRows", 10).
  trigger(Trigger.ProcessingTime(10.seconds)).
  queryName("rate-console").
  start