docs: @SuppressWarnings("checkstyle:magicnumber")
      private void firstHeartbeat(long firstHeartbeatEstimateMillis) {
          long stdDeviationMillis = firstHeartbeatEstimateMillis / 4;
          heartbeatHistory.add(firstHeartbeatEstimateMillis - stdDeviationMillis);
          heartbeatHistory.add(firstHeartbeatEstimateMillis + stdDeviationMillis);
      }