code: private void rollBlocksScheduled(long now) {
      if ((now - lastBlocksScheduledRollTime) > 
          BLOCKS_SCHEDULED_ROLL_INTERVAL) {
        prevApproxBlocksScheduled = currApproxBlocksScheduled;
        currApproxBlocksScheduled = 0;
        lastBlocksScheduledRollTime = now;
      }
    }
docs: Adjusts curr and prev number of blocks scheduled every few minutes.