Where do I see fitField.dataLabel in charts?

<resources>
  <fitContributions>

    <fitField id="0"
      displayInChart="true"
      displayInActivityLaps="false"
      displayInActivitySummary="false"
      sortOrder="0"
      precision="0"
      chartTitle="@Strings.fitCurrentHeartRateChartTitle"
      dataLabel="@Strings.fitCurrentHeartRateLabel"
      unitLabel="@Strings.fitBpm"
      fillColor="#f25b0a" />

I don't understand why dataLabel is required in this case. Where can I see the data label?

For other fields, where displayInActivityLaps or displayInActivitySummary is true there I see it in GCM and GCW in the stats of the activity. But for the above field I can't find anywhere it is didplayed.