What must updated null flag updated or conflict flag updated?

Question

I work on SQL server 2012 .really I don't understand what statement below do updatedand when
when NullFlag updated
and
when conflict flag updated

can you explain to me according to sample below

result of query data details rows without grouping

Masked_ID DocumentID PartID NULLCount
 29283933 76724 31345983 NULL
 29283933 76724 31345984 NULL
 29283933 76724 31345985 NULL
 29283933 76724 31345986 NULL
 29283933 NULL NULL 1
 29283933 NULL NULL 1
 29283933 76724 31345989 NULL
 29283933 NULL NULL 1
 29283933 NULL NULL 1
 29283933 76724 31345992 NULL

 UPDATE FFFF
 SET
 Conflictflag= IIF((NotNULL+NuLLCount)<>RowsCount AND Ex.MaskExceptionID IS NULL ,CONCAT(Conflictflag,'PCN','|'),Conflictflag),
 NULLflag=IIF((NotNULL+NuLLCount)=RowsCount AND NuLLCount>0 AND NULEX.NULLExceptionID IS NULL,CONCAT(NULLflag,'PCN','|'),NULLflag)
 FROM
 (
 --SELECT Masked_ID,SUM(CNT)/COUNT(DocumentID) AS NotNULL ,SUM(NULLCount)AS NuLLCount
 SELECT Masked_ID,SUM(CNT)/nullif(COUNT(DocumentID),0) AS NotNULL ,SUM(NULLCount)AS NuLLCount
  FROM (
  SELECT FF.Masked_ID,  LC.DocumentID,
  COUNT(DISTINCT LC.PartID) AS CNT,
  COUNT( CASE WHEN DocumentID IS NULL THEN 1 ELSE NULL END )NULLCount
  FROM ExtractReports.dbo.MultiMask FF
  INNER JOIN Parts.Nop_Part ptt WITH(NOLOCK) ON ptt.Masked_ID=ff.Masked_ID
  LEFT JOIN PCN.DocumentParts LC WITH(NOLOCK) ON ptt.PartID=LC.PartID
  WHERE FF.PCNs LIKE '%|%'
  GROUP BY FF.Masked_ID ,LC.DocumentID
  )DD
  GROUP BY DD.Masked_ID
  ) DDFF
  INNER JOIN  ExtractReports.dbo.MultiMask FFFF ON  DDFF.Masked_ID=FFFF.Masked_ID
  LEFT JOIN [ConflictReport].dbo.MaskExceptions EX ON EX.MaskID=FFFF.Masked_ID AND EX.FunctionName='PCN'
  LEFT JOIN [ConflictReport].dbo.NULLExceptions NULEX ON NULEX.MaskID=FFFF.Masked_ID AND NULEX.FunctionName='PCN'
  WHERE
  FFFF.PCNs LIKE '%|%'

on case of data above what must updated Null flag or conflict flag
and why
can you please help me