private long calculateWriteCapacityUnitDiff(final long actualSize, final long estimateSize) {
    return calculateWriteCapacityUnit(actualSize) - calculateWriteCapacityUnit(estimateSize);
  }
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