Refresh XML column of table in SQL Server 2008R2

I have a table named DateRule in sql server 2008R2 and I am trying to update the value of an XML column but it is not working as expected.

• DateRuleId: 40
• Description: 2 months after the launch date.

• DateRuleXml:

          <Daterule>
              <Type>Timespan</Type>
              <months>2</months>
              <days>0</days>
              <hours>0</hours>
              <minutes>0</minutes>
              <seconds>0</seconds>
              <After>1</After>
              <Reference>1</Reference>
          </Daterule> 
  
        
  
          
          
          
        
  
      

I am trying to run the following query:

update centralq3.wf.DateRule
set DateRuleXml.modify('replace value of (/Daterule/@Reference)[1] with "6"')
where DateRuleId = 40

      

        
        
        
      

    

AND:

update centralq3.wf.DateRule
set DateRuleXml.modify('replace value of (//@Reference)[1] with "6"')
where DateRuleId = 40

      

        
        
        
      

    

They both succeeded and said (1 line (s) affected) but the Reference value does not change. What am I doing wrong? I know there are many questions regarding this but did not help me.

Change !! Answer:

UPDATE centralq3.wf.DateRule
SET DateRuleXml.modify('replace value of (/Daterule/Reference[1]/text())[1] with "6"')
WHERE DateRuleId = 40