Resource notificationTime

When requested via PHP a resource document looks like the below.
Everything seems obvious except "notificationTime".  I don't see what
this key corresponds to,  is this value of any use?

XML_RPC_Value Object ( 
  [me] => Array (  [struct] => Array ( [name] => XML_RPC_Value Object ( 
    [me] => Array ( 
      [string] => Conference Phone ) [mytype] => 1 ) 
      [emailSubject] => XML_RPC_Value Object ( [me] => Array ( [string]
=> OGoResource: Conference Phone ) [mytype] => 1 ) 
      [email] => XML_RPC_Value Object ( [me] => Array ( [string] =>
cisstaff@xxxxxxxxxxxxxxxx ) [mytype] => 1 ) 
      [category] => XML_RPC_Value Object ( [me] => Array ( [string] =>
IT Equipment ) [mytype] => 1 ) 
      [objectVersion] => XML_RPC_Value Object ( [me] => Array ( [int] =>
1 ) [mytype] => 1 ) 
      [id] => XML_RPC_Value Object ( [me] => Array ( [string] =>
skyrix://throw.morrison.iserv.net/morrisonOGo/465990 ) [mytype] => 1 ) 
      [notificationTime] => XML_RPC_Value Object ( [me] => Array
( [string] => ) [
    mytype] => 1 ) ) ) 
 [mytype] => 3 )

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