private long estimateConsume(final OperationType type, int numReqs, long avgSize) {
    if (numReqs > 0) {
      return avgSize * numReqs;
    }
    return 0;
  }
Update estimate quota(read/write size/capacityUnits) which will be consumed
@param scanRequest                     the scan to be executed
@param maxScannerResultSize            the maximum bytes to be returned by the scanner
@param maxBlockBytesScanned            the maximum bytes scanned in a single RPC call by the
                                       scanner
@param prevBlockBytesScannedDifference the difference between BBS of the previous two next
                                       calls
hbase-server/src/main/java/org/apache/hadoop/hbase/quotas/DefaultOperationQuota.java